I ran across your site today through my search engine, when looking for a stone called "spotted chalcedony". I have been searching for it with no luck. I am attaching a picture of it, and hoping you can tell me what it is, or where I can find it. Apparently, it goes by a different name. I just don't know. I love your site and want to take advantage of your educational features. Thank you very much, I can't wait to hear from you! Raoul, USA
"Spotted Chalcedony" is not a standard or accepted name in the gem industry -- in fact, the name is a contradiction, as chalcedonies are not spotted. The gem picture you sent, then, does not look like any true chalcedony that I know of.
Chalcedony, in the gem market, is any translucent, single color form of cryptocrystalline quartz. Examples are blue chalcedony, chrysoprase and carnelian. If the stones you have are indeed a form of quartz they might more reasonably be called "brecciated jasper". That is the geological term for when a matrix material solidifies into rock with chunks of other preformed minerals in it (brecciation) -- this effect can also be simulated by man, so my first concern would be if your stones are natural or man-made.
Unfortunately it is impossible to determine the identity of a gem by simply looking at it (or worse yet a photo of it) -- tests must always be done to determine identity. If there is a GIA certified jeweler/gemologist in your area, you could get it tested.
Here's a link to my photo-essay on chalcedony:
What is the difference between A Sunset Sapphire and a Tanzanian Ruby? Thanks!...Claire, USA.
The whole business of gem names can be fraught with peril for the seasoned collector, and the new enthusiast as well. I have never heard of "sunset" sapphire, but any names like that are usually trade names -- it is OK with the FCC if a seller wants to "romance the stone" by giving it a special name -- hence Rose D' France is used to improve the marketability of very pale amethyst. As long as the gem in question actually IS sapphire (either enhanced or unenhanced) the term sapphire can be given any adjective the seller wants. A quick Google search on sunset sapphire just turned up a couple of diffusion enhanced stones similar in color to natural Padparashah sapphire. By law, if the gem is man made sapphire, then that must be included in the name, so the ones you've seen should be natural origin stones.
Tanzanian, if used properly with ruby should simply mean origin, as opposed to Vietnamese, Burmese or some other locale. But even there, exceptions apply -- it is common to use the term "Siberian" in describing amethyst and "Persian" in describing the color of fine amethyst and turquoise, respectively even though the gems most likely come from newer, more available deposits.My answer is predicated on the sellers being honest and knowing and following the law -- unfortunately that is not always the case. :-(
I have seen much Tashmarine but really can't find any information on it. Can you help me? How rare is this stone? Thank you for your time... Sean, USA
Tashmarine is a trade name for a variety of diopside that is not dark green like chrome diopside, but light green. My impression and personal opinion, as I have not researched it thoroughly, is that it is a yet another case of a marketer trying to "romance the stone". Sometimes when there are deposits of a less saleable type of some popular gem, the developers and marketers of the resource try to create excitement by giving it a fancy, sometimes exotic name and promoting it highly -- often times this fails as the material just isn't all that attractive, and doesn't find a public. Other times, it works splendidly, as it did in case of pale blue lapis from Chile with lots of white calcite --which found a market as "denim lapis", or very light amethyst, which got a niche as "Rose d' France" amethyst. Home shopping channels and internet auctions sites can be very important in promoting a strategy of this type. My impression is not so much that Tashmarine is rare, but just that it is unknown to the general gem buying public.
Tashmarine, if you like the color, should be in the value ball park of chrome diopside -- and would have chrome diopsides drawbacks of cleavability and softness making it OK for earrings and pendants, but a poor choice for rings. I, personally, would not pay a premium for it
Here's a link to my pictoral essay on chrome diopside:
Chrome Diopside Essay
I was reading your G.O.M. article on amethyst published in 2007. It notes that large stones from Uruguay or Zambia can become too dark. My question is, how do you know if an amethyst is too dark? I know that the dark variety is most coveted. I assumed that a nice violet with some areas too dark to see through was what you expected from the high grade stuff, like your pictures of "Siberian" amethyst in the article. Thank you for the time. Don...USA
Thank you for visiting my site. I'm afraid my answer will be rather long winded, and ultimately not satisfactory. (For the benefit of my other readers I'll include a link to the essay to which you are referring).
GIA and other gemological organizations have published color grading scales based on a standard set of color descriptors. Hue, saturation and tone are those most often used. Hue is the basic "color" of a gem -- its spectral value (red, orange, yellow, green, blue, violet, etc), saturation describes how much the basic hue is modified by "muddying" amounts of brown or grey, and tone describes how light or dark it is. The tones range from pale (almost colorless) to very dark (looks black except with high intensity light). In general, the most desirable gems fall into the category of medium to medium dark in their tone. Some gem species cannot be evaluated this way as all specimens are naturally light in color (think Morganite) or naturally dark (ex = almandite garnet), but, for the majority of species, a medium dark tone is ideal. Medium dark could be described as "showing rich color in normal lighting, but not looking black". Of course this also must be combined with strong saturation to command top prices.
There are several factors which control how dark a gem is: among them are its individual chemistry and physics, its size (bigger gems absorb more light and are darker) and its cut (shallow, brilliant cuts and large tables decrease "darkness", deep step cuts and small tables increase it. Certain enhancements such as heating or irradiation can lighten or darken tone. Add to this basic information, the concept of "taste". I cannot tell YOU what is too dark -- except to say what is "too dark" for me. If the stone looks black in most lights, it is too dark for me, but some people may prefer a gem of that tone.
What's the difference between a gem, i.e., a diamond, being "heat treated" versus one that's been "irradiated"?...Veronica, USA.
Heat treating, if accurately reported, refers only to heating a cut gem or its rough in a "furnace" either in an oxygen-rich or oxygen poor environment. The regimens for heat treating vary with the material and the desired result. The color or clarity changes are almost always permanent and derive from a chemical change that occurs in the makeup of the gem. An example is blue, white or red zircon which starts out as natural color orangey brown rough and depending on the regimen (temperature, time, atmosphere) acquires the more marketable colors.
Irradiation refers to subjecting a gemstone to high energy radiation or particles such that it's chemistry remains the same, but its crystalline structure is affected so as to change its properties of light absorption, hence its color. There are various radiation treatments in use and often the irradiation must be followed by heating to either stabilize the color change or to create additional color change. Examples are blue topaz which starts out as colorless rough, is irradiated to an unstable brown and then heated to a stable blue. Another example is salt waterpearls which can be irradiated to turn them from white to a dark, silvery grey. In a few cases, some types of irradiated gems can lose their new colors over time or with exposure to sunlight.
As long as they are disclosed including care and durability factors, both types of treatment are considered quite acceptable in the gem marketplace and have only moderate effect on a gem's value as compared to an unenhanced specimen. That cannot be said of certain, more invasive or more fragile treatments such as glass filling, laser drilling or surface coating which greatly affect the value of a gem.
Hi! I am from the Philippines. May I know how to detect a "Diamond Hybrid" against real diamond gemstone. Thank you....Josephine, The Philippines
Since a "Diamond Hybrid" has a core of non-diamond with a thin diamond coating applied by some kind of vapor deposition process, it is mostly not diamond. The simplest and most direct test would be specific gravity -- usually the core of such stones is CZ which is much heavier per unit than diamond, sometimes it is white sapphire which is also heavier.
I came across your site while doing some research for a question that has come up on the formation of inclusions in Quartz crystals. I'm glad I found you, because your site gives me an opportunity to discover minerals from a scientific perspective. Thanks for making it available.
I work with crystals from a metaphysical perspective. I have a retail business finding crystals for people. I deal mostly with raw or polished points and tumbled stones. There is a crystal I've been offering as a Titanium Gas Phantom crystal - which is what it has been called by many, including those I got them from.
Someone recently got in touch with me and informed me that it is impossible to have Titanium Gas inclusions in a crystal because the Titanium changes into a gas at very high temperatures - higher than the temps at which crystal solidifies. One of my suppliers gave me a geological report which shows that there are Titanium inclusions.
Are you able to shed some light on this subject. From a metaphysical perspective the stone is valuable for its energetic properties rather than its physical properties. But I am interested to know as much about a stone's formation and inclusions ... and as well I want to be as honest as possible in representing them to my customers...Smadar....Canada.
I appreciate your wanting to accurately describe your wares to your customers, that is admirable, and all too rare in gem commerce.
Inclusions can be pre-existing and engulfed by a developing crystal, or they can form within as it crystalizes -- in some cases they can even form afterward due to pressure or heat applied to the finished crystal. I am not expert enough in gemstone inclusions to help you in more than the most general way. These links will take you two essays, one on magnification and the other on gem formation, both of which include information on inclusions.
Although I personally I have not run across any scientific evidence for any property or effect of a gemstone or crystal, other than that explained by its physical and chemical nature, I do understand the power of belief, and that many people would disagree with me. Even skeptical types seem to enjoy the fun of learning about this kind of gemstone lore, and it is good to know that there is at least one practitioner within that field who is attempting to verify some aspects of the information they offer.
Hi there. In regards to your Gemology course: do you offer a summer short course, or any short courses for that matter?... Nathan, USA.
I presume you are talking about my official "for credit" Geology 115 course through CSN (College of Southern Nevada), and in that case, unfortunately, the answer is no. I do not teach during the summer at present. Many of the normally 15 week courses at CSN, however, are taught in a compressed format of 5 or 7 weeks during the summer sessions.
My free gemology course, www.bwsmigel.info can be taken in any time frame that you wish as there is no time-table. You could considerably shorten the content by reading only the web lectures and skipping the essays.
Could you please tell me what is the rarest gemstone? My friend said it was an emerald...Monica, England
I'm afraid your friend is mistaken. Although emerald is not the world's most common gem, it is not as rare as dozens of other gems. It is difficult to say which gemstone IS the rarest, as there is no hard and fast definition of exactly what a gemstone is, and new sources being discovered or old ones being depleted, can change the rarity of any gem.
In the first lesson of my free gemology course, entitled "Basic Terms", there is a discussion of the concept of rarity as it applies to gemstones. In particular, I make a distinction between gems that have inherent rarity versus those that have relative rarity. Within that lecture there is also a link to a website that has a list of what that author considers to be the world's 10 rarest gemstones along with his reasoning on each.
Here is a link to the lecture: http://www.bwsmigel.info/Lessons1and2/DEBasicTerms.html
And one to the "10 Rarest" list: http://www.curiousnotions.com/gemstones/index.asp
I have a Paraiba Ice (simulated) stone 2.58 ct 10X10mm Trillion. Can you help me get an honest value of this stone?...Betty, Oregon
Generally with sythetic simulated stones (which I believe yours to be), the value is in the cutting and/or the jewelry mounting. The synthetic simulant stones have little intrinsic value. The reason is that they have no rarity -- they can be made in whatever quantity the market demands. There are some exceptions, for example, in the case where the only method for making a given synthetic is itself costly and time consuming (as in the case of synthetic Alexandrite or CVD (Chemical Vapor Deposition) synthetic diamonds), but the value even in these cases is but a fraction of that of the natural product. So far as I know "ice" stones are generally cubic zirconia, which can be made in almost any color -- the current market value colorless CZ rough is less than 5 cents per carat, with colored forms a bit higher.
Since the marketer is not calling the stone a Paraiba tourmaline, but rather Paraiba "Ice", that falls under the category of a trade name. A seller can call a stone anything they want as long as they don't misrepresent it. Since the term Paraiba is so strongly associated with very expensive and beautiful tourmalines, they may be erring ethically to use it, but they are well within the Law to do so.
I was given a ring that I was told was ruby, but I don't know if it is. It is approx. 10 cts. plus and is lightly included. It's a gent's ring: a square cusion cut with a flat table. There are very faint lines on it that run the shape of each facet-not circular. Someone told me that if it was synthetic, they would run circular, he said my lines were created by a grinding wheel. Also,I put it under a blacklight, and it glowed in the most beautiful color. Where can I go for an honest appraisal?...Douglas, New York
A 10 carat red, ruby-like stone that glows in ultraviolet light is most likely a ruby, but almost certainly a synthetic one. The chances of finding a Burmese (the kind that glow) natural ruby of 10 carats that doesn't cost millions of dollars is slim.
Your friend is correct in saying that curved lines are the sign of a sythetic, but that applies only to the oldest and cheapest method of synthetic ruby manufacture (flame fusion) which goes back to the early 20th Century. Alternately, some newer synthetic rubies are grown by processes that do not produce curved growth lines, but result in natural looking color zoning and angular growth lines instead.
On the off chance that somehow you have acquired a fine natural stone worth a great deal of money, or if your curiosity just must be satisfied, you should look for a Certified Gemologist/Appraiser. A person needs to have BOTH credentials to make a good call on gems/jewelry as most general appaisers don't have specialized enough knowledge in gems, and most gemologists do not have the expertise required to set a value.
I am looking forward to studying your website, and getting a better knowledge of my gem collecting hobby. There is one aspect that I would like to explore as well and that is gem cutting (lapidary?). Please advise what is the best way to learn how to facet rough into gems...Candace, USA
A good place to start is to read my essay on Faceting: http://www.bwsmigel.info/GEOL.115.ESSAYS/Considering.Faceting.html
As it recommends, your best bet is to find a mentor at a local gem or rock hounding club that can let you do some hands-on trials.
What does the gem-enhancement code "S" mean? I don't see it defined on your code-glossary page, though perhaps I missed it. I saw it on some ammolites on your site....Jim, New York
The official code for the process used on ammolite, and sometimes other gems like turquoise and coral, is "I" for Impregnation, in common usage, however, the term stabilization which I slipped up and used instead, (S) is identical. The process of impregnation aka stabilization, consists of infusing a colorless resin (usually under a vacuum assist) into a porous gem to make it harder and more duable, or easier to polish, or even as in the case of turquoise, to minimize discoloration from wear. It falls into that category of "generally accepted" within the industry (as long as it is disclosed), and does not have a drastic effect on gem value. In the case of ammolite, other than making a doublet or triplet, it is virtually the only way that this delicate, but beautiful, gem can be used in jewelry. Thanks for bringing that inconsistency on my site to my attention.
I am writing from Singapore. I am currently wearing a rutilated quartz pendant & a watermelon tourmaline pendant. Can you enlighten me as yo how will these two pendants help me in terms of everything in my life?...Ann, Singapore.
Although I, personally, do not subscribe to any mystical or metaphysical properties of gemstones, having never seen any properly controlled scientific studies that demonstrate them, there are many who disagree with me. The history of gemstones is rich with lore of a mystical and metaphysical kind, which I find enjoyable, not as fact, but as fancy. To my way of thinking, the scientific and aesthetic aspects of gemstones provide sufficient wonder and joy. You can easily, however, find kindred spirits by entering "metaphysical + gemstones" into Google or some other search engine. I hope you continue to enjoy your gemstone jewelry.
I am considering taking your free course to become certified and, plan to start a small business (I'm retired and love rockhounding and days in the field). I was viewing kits for gemology and ran across a website sellling gem and lapidary equipment, and they have kits for around $ 1,000.00 and $ 2.000.00 called "professional" gem kits. They claim everything I need is there. Would you concur that that is pretty much enough for a lapidary business start kit or would you have me consider some other options you are familiar with. Thanks....Richard, USA.
I'm glad that you are interested in taking my free course, however, I must point out that you do NOT receive any kind of certification for completing. I'm simply making the information available to promote knowledge in gemology to whomever is interested. If you want a credential you'll need to take courses from an organization which awards a diploma or certificate like: GIA, IGS or ISG.
I have dealt with the website you mention, and the equipment I've gotten there is first rate and reasonably priced. Whether it is "all you need" would depend on what you plan to do. Call and talk to the owner, who will be able to guide you in the selection of equipment based on your needs.
You recently answered a quesion for me, thank you, now I have another one for you. I also purchased (in Tucson) a lovely Larimar ring, but don't know anything about the stone except that it is a lovely turquoise colour. Is it hard or soft? Natural colour? Only found in the Caribbean, as they claimed? I found some info on a website (www.caribbeanlarimar.com), but you never know how much is hype...Shirley, Canada
It just so happens that I wrote a photo essay on Larimar pretty recently, so I'll share that with you. If you have any additional quesitons -- feel free to follow up.
Is there a way to test amethyst..I have a bracelet with amethyst set in 14k and someone is interested in this bracelet and wants me to take this and have the stones tested......I feel sure they are real because it came from an estate...Darlene, USA
It is relatively easy to separate amethyst from natural and man made simulants, like glass, purple laboratory sapphire, etc. What is difficult and rather expensive and time consuming is to test natural vs synthetic amethyst. If the piece is very old it might be glass which was very popular in earlier years when amethyst was much rarer than it is now -- simple tests that jeweler can do can easily detect glass.
The synthetic version has been on the market for several decades and was initially relatively easy to discriminate, but in the last twenty years a new manufacturing process has made synthetic amethyst especially hard to detect without a great deal of experience and expertise. You or your potential buyer would have to pay a gemological lab to test the gems to rule out modern synthetics -- I'm not sure the price of the item, would justify the cost.
Hi, my name is Cindy, and I saw a posting online with information you were giving to somebody regarding a refractometer. I was hoping you might be able to help me with a question. I am not a jeweler. I have a box of items that belonged to a jeweler, including the Duplex II refractometer. Thing is, it appears in good shape but the glass portion on top, inset in the chrome, is yellowed. Is this normal? I want to sell it but am afraid to list it if it is defective; I have no idea of its age or handling. Do you know if it is normal or not? Also in the box is a vintage Leveridge Gauge setŠare these non-electronic type gauges still used by jewelers?...Cindy, USA
You might contact GIA (www.gia.edu) and via serial number, they may be able to give you the age of the item.
Yes, Leveridge gauges are still used, and as long as the glass hemicylinder of the Duplex II is not cracked or scratched, the oxidized coating on it could be polished away and it should be as good as new. Brand new ones are in the range of $800, and they operate just the same as the older ones, so I think you'd find a ready buyer for it, even if it was somewhat vintage.
Recently I bought a necklace, which looks very much like it's antique and made of amber. Since it was a garage sale, and the price was just ridiculuous, I did not hesitate to buy it. Is there any way to distinguish a real amber from an imitation? The beads of the necklace are 2cm diameter size, perfect spherical shape, have air bubbles and some other inclusions, and are amber (honey) color. The only thing that makes me doubt that it is real is that beads have some dark strips on the surface. The clasp looks like it is made of silver I'd appreciate any information on the real amber identification. Thank you..Tamara, USA.
Amber is most commonly imitated by either plastic, or in some cases a material called "amberoid" which consists of powder and trimmings from amber processing which has been heated and pressed together. Since plastic is light, and warm to the touch and has a hollow sound when tapped on a hard surface and so does amber, it is difficult to distinguish the two without destructive testing If you had access to a single, loose bead and the right equipment you could do a specific gravity (density) test which might help -- amber is usually lighter than the plastics commonly used to imitate it. The dark markings are common to natural amber so I wouldn't worry about them, unless they are uniform which might indicate some kind of stamping or processing used to make the beads. The test I'm going to suggest to you is technically "destructive" in that you must ruin a bit of the material to perform it, but it is reliable and you can confine the damage to a small, inconspicuous spot.
Take a substantial sized sewing needle and heat it (wearing protective gloves) so that the tip is red hot, apply the red hot tip to a small spot on the bead you are testing, a small puff of smoke should be produced -- waft the smoke toward your nose. If you smell a "piney" "resiny" or turpentine-like smell, you have amber or amberoid -- if you get the chemically acrid smell of burning plastic instead, then you have your answer. If you have access to a 10x loupe and good lighting, check the beads for internal uniformity and signs of "joins" between pieces which would indicated amberoid, distinctive inclusions in the various beads, and lack of "seams" would indicate real amber. I'd be interested to know how your test turns out.
I am surprised by the fact that my fingers turn black if I wear diamond rings in winters!!! If I wear non-diamond rings like zirconia or other stones they are perfectly ok!! The rings whether diamond or non-diamond are with 21carat gold. Can you tell me why does it happen??...Deepti, India
The skin surface varies in acidity (pH) depending on gender, age, diet, stress, state of health, hormone levels and other factors. The more acid the skin surface, the more likely the copper in any alloy of gold will be to react and create dark green to black sulfur compounds. The effect is generally less with higher karat golds as there is less copper present. What you are seeing is probably due to the fact that diamonds are generally put in higher karat gold settings than CZs. It might also be the setting itself where more metal is in direct contact with your skin in the ones with CZs and less with diamonds. Although you say all the settings are the same purity, I would doubt perhaps the quality control on the CZ mounts.
I know of no chemical or physical phenomenon relating to the the gem itself that has anything to do with these finger marks.
One simple remedy you can use is to paint the inside of the metal surface of the ring band with clear lacquer (nail polish will work). This will not harm the gold or show from the front, but will keep your skin out of direct contact with the metal. You'll need to renew the coating periodically.
Thank you for all the information on your web site. I love gems and learning about them. How do you tell if a ruby is from Burma or if it is from Thailand? Is it true the way to tell a Burma ruby is to see if it glows under a black light? How important is it for the value? My husband purchased one for me for Christmas its almost 8 cts pear shape. Thanks for helping... Jeanette, USA
Rubies that contain a sufficient amount of chromium without any iron will fluoresce brightly under UV light. In general rubies from Thailand or Vietnam or Africa have iron in them which dampens the fluorescence, while those from Burma have chromium alone. This is not a hard and fast rule, though, as individual mine sites and even individual gem deposits differ in their trace elements. Some of the most brightly glowing rubies are the synthetic ones, as it is very easy to put an ideal amount of chromium and exclude the iron under lab conditions.
Any large natural Burmese that is relatively clean is highly valuable -- most would come with a certificate indicating natural origin, any enhancements and perhaps listing probable geographic origin. An 8 ct. stone is VERY large indeed -- depending on the color and clarity such stones, if of natural origin, could bring hundreds of thousands of dollars.
Hello! I have a 2 ct marquis diamond that has a very small chip on one of the tips (not visible unless seen under magnification). Anyway, I was wondering if it were possible for the diamond to be recut into a circle?..Melissa, USA
Certainly diamonds can be recut, but they can also be repaired -- if you were to recut this one into a round, you'd lose a lot of weight though -- perhaps as much as 35 - 50% which would substantially alter the value of the stone. If the chip is small why not just have it repaired, keep the marquis shape and retain most of the stone's value?
Depending on where you live a jeweler may have a resident diamond cutter, but if not, most larger shops have contacts with independent cutters who will quote you a price on the repair or recut, and who will handle the shipping etc for you.
My name is Jaume and I live in Bangkok. I study in GIA, and I see you on the internet. I'm interested to find some Coral because I'm learning also to cut, and is a soft stone that I want to start to work. I want to know if with your experience you can help me!!!! I hear that from China and Indonesia is possible to get some coral. Any recommendation for get rough coral? Well, wish you a happy new year...Jaume, Bangkok
Hello Jaume: I'm afraid I have not purchased much coral rough and have no particular suppliers to recommend. There are many types of corals -- stoney, spongey, proteinaceous, and all of them can be dyed to a red color, so you need to be careful. Perhaps this essay on coral will help you in your selections.
Hi! Can colorless topaz test positive as being a diamond, with the copper probe?... Linda, Australia.
I am not familiar with the terminology "copper probe" test, but let me assume that you mean a device that uses a probe to measure the thermal inertia and/or electrical conductance of a gem. The standard diamond tester does the first and the new generation diamond/Moissanite tester does both. Topaz will test negative with either of these devices as its thermal inertia is dramatically different from diamond.
What generic product can I use to clean a pair of mystic topaz white gold earrings?...Linda, US
I would recommend a dishwashing detergent and warm water mixture with a very soft brush -- although topaz is, in general, a fairly hard stone, unlikely to be easily scratched, the microthin metallic layer that has been deposited on it to create the "mystic" effect is quite fragile. Let the earrings soak a bit, then gently use the soft brush around the prongs and underneath the settings -- rinse well with plain water and blot dry (do not rub) with a soft cloth.
Can you tell me how I could go about having a piece of jewellery made from Taaffeite? My interest in the stone is partly sentimental - my maiden name was Taaffe - and as such I am no expert. I notice that you advise that Tanzanite is too soft for every day rings, and I have read elsewhere that Taaffeite is similar to Tanzanite - what sort of jewellery would Taaffeite lend itself to best? Many thanks... Emma, UK.
I'm not sure in what way your source is comparing Taaffeite to Tanzanite as I do not see much similarity. Taaffeite, unlike Tanzanite, shows no cleavage so it is tough, and it has a hardness of 8 - 8.5 (compared to Tanzanite's @ 6.5). It has similar properties to spinel which is an excellent ring stone -- I wouldn't mount any gem softer than H = 9 in a high prong setting, and wear it 24/7/365 as an engagement ring, but for normal use, there are no worries with Taaffeite.
In general, bezel settings are more protective than those with prongs, and if you have diamonds or metal raised slightly higher than the Taaffeite you might even get away with daily wear. Congratulations on owning one of the world's rarest and most collectable gemstones!
Could you give me any information on iris or rainbow rhinestones..or what rainbow quartz looks
I'm not sure of that terminology, so I will give you my best guesses. In today's market and over the last several decades, a "rhinestone" is usually glass with some kind of foil or paint applied to the back surface that increases reflectivity, although a century ago, they were made of colorless quartz that was foil-backed. Iris quartz is a type of agate with micro cleavages that create bands of iridescence. Rainbow quartz could be similar to what today is called "Aqua Aura" quartz which has a thin metal vapor deposited on it to cause iridescence.
Is platinum more malleable than gold? I know white gold is harder, and gold is malleable, In reading I just can't find anything out about platinum being malleable...Elaine, USA
Yes, platinum is known for both its durability and its malleability. Those intricate Edwardian filigree designs in platinum showcase that property. My jeweler, who works with all the precious metals says platinum moves "like butter". On the other side, working platinum requires special high temperature soldering and melting techniques and it is horrendously expensive due both to its inherent cost, and to the fact that it is so dense that it takes a greater weight of platinum to create any design, than would be required in gold.
Hello. I just discovered your website and I'm very excited. I've been looking for what my grandmother called a smokey topaz stone. My grandmother always wore this huge, beautiful "smokey topaz" ring that, since she passed on, my mother wears. My sister's husband recently bought her one as a way to honor grandmother as well, and I would also like to find one. For some reason I can't seem to find any stones called "smokey" ?? Going through your site makes me wonder if there is even a topaz called "smokey"? My grandmother's is yellowish/brown... on the lighter side. My sister's is more brownish. Can you please enlighten me as to the real name of such a topaz? I greatly appreciate your help, and really enjoyed your website. Thank you, Christine...USA
Thanks for visiting the site, and for your question and kind words. This is one I've answered before, but it comes up so often that it bears occasionally repeating. There is no gemstone called "smokey topaz". That term was used (and in some areas still is) to mean smokey quartz. The confusion probably initially arose as a translation lapse. In Brazil where most of the smokey quartz is mined, the term ''topazios" means yellow. So packets of smokey toned yellowish quartz like that in your grandmother's ring could have been imported with that terminology, and US dealers simply mis-translated. The "misnomer" thrived in the market place for another reason. Topaz is a rarer and more expensive stone than quartz, so by calling a stone "smokey topaz" rather than smokey quartz, more money could be charged for it. If you search my site and internet in general for "smokey quartz" you'll find a range of affordable pecimens in a variety of tones and hues.
I love amethyst and have several pieces. I was told by a gentleman that you could tell whether or not it was genuine by holding it to your cheek and feeling if it is "cold" Do you know what he is talking about? I have several pieces of imitation amethyst, and cannot tell the difference between it and the ring I had made from an amethyst quartz....Patty, USA.
What he is probably referring to is a property called "thermal inertia", the rate at which different materials transfer heat. In general, crystalline materials have low thermal inertia and therefore feel cool to the touch at most room temperatures, glass is a bit warmer, but unless you are quite experienced, the difference is not that noticeable -- plastic is quite warm to the touch. If your gem is cold it could be a crystalline gem like amethyst, glass or even synthetic amethyst (which is just like nature's crystal), so I think the only case where his test would work reliably would be the case of a plastic gem imitation.
I recently purchased a Tanzanite ring from Tiffany's and wore it three times, and it already has a scratch. It was sent in to get resized, could something have happened when it was sized? Or did it get scratched from being cleaned at Tiffany's? Or did I do something? My husband and I are so confused. And is there a way to fix the scratch?...Gina, California.
Sadly, your story does not surprise me. Tanzanite is a very poor ring stone, it is both soft, and cleaves easily. Especially if the ring is worn daily, and is in a high mounting, scratches and chips are inevitable. Tanzanite is best reserved for occasional wear, in protectively set rings or better,yet, as earrings and pendants. You can have a jeweler get it repolished for you but the original problem will still be there -- my advice would be to have the gem reset in a pendant or the ring setting redesigned to be protective and to wear the ring carefully. I have a friend who does repair work for jewelers who told me that he could make a good living simply from repolishing and recutting Tanzanites that had been damaged in rings.
To me, the way the commercial jewelry community pushes Tanzanite as a ring stone is unconscionable.
What do you know about the colored diamonds sold in Thailand? Are they all irradiated diamonds? Say, a cognac colored diamond, is that an irradiated diamond? Also they say most of the rubies now have lead glass fillings. Is there a difference between residues in the ruby, say moderate in factures and minor in cavities? Is that considered normal as a result of the heating process. What is the difference between the two (lead glass fillings, and residues)?...Shirley, USA.
I'm afraid that since I do not deal in diamonds I know little of a specific nature. Of course, cognac colored diamonds do occur naturally, but so far as I know the vast majority in the marketplace today are created from off color whites through irradiation and then heating. Personally, I would assume any yellow to brown diamond to be enhanced without a certificate from a well known lab certifying natural color.
As far as rubies and their fillers, your question gets right to the heart of what diminishes value in an enhanced stone. Routine enhancements, like simple heating and minor amounts of silica or glass-like material that migrates into tiny fissures during heating detract very little from a ruby's value. Glass infilling, however is in that category (along with laser drilling and diffusion coloring) as to be an "exotic" treatment which greatly diminishes value. With the infilling process large surface and interior cavities are filled with molten glass and then when the stone is faceted it looks many grades better in clarity than it did before -- such areas can be detected with a microscope or even by a trained eye (due to luster and hardness differences). The glass makes the ruby much less durable as it can be etched by jeweler's solutions and melted by torch heat and scratched easily, not to mention that a customer who pays for 2 ct of ruby might be paying ruby price for .5 ct of glass along with it. So the short answer is pretty much, residues are OK, fillers are not.
What is Sunrise topaz? Is it a natural stone or is it colorless topaz which has been heat-treated or dyed? ...Tamara, USA.
Diffused topazes have been given all sorts of names -- like "Sunset" to reflect their lovely, but skin deep color, and they are all just trade names. The treatment is not simple heating nor is it dyeing. Under incredibly high temperatures the cut topaz gems (probably colorless) have been subjected to near melting which makes the normally impervious surface open up slightly - a chemical which bonds with the topaz mineral and gives it color, penetrates to a microthin layer making the stone appear to be that color all the way through. There nothing wrong with diffusion treated stones, they can be quite pretty. And as long as the diffusion is disclosed to the buyer (along with proper care instructions), and the price is appropriate everyone is happy. In this case the appropriate price is just slightly higher than that of white topaz. To answer your question, then, yes, it is natural stone (natural-origin topaz, not synthetic), but it has been enhanced to create an unnatural, surface-only color.
I love your site. I have no formal training but I am a "Gemstone Junkie" I recently obtained a Certified Natural Taaffeite .46 ct with a pale pink color. I was wondering about wholesale prices on this gem. I can't seem to find much info out there on actual value....Emily, Nevada.
Thank you for visiting my site and for your kind compliment. With the rarest of gems, like Taaffeite, there are simply no established price ranges. It's literally a case of "the gem is worth what the highest bidder will pay for it". (Like with rare paintings, coins, stamps or antique autos). I'm sorry, I know that sounds like a cop out -- but that is the way it is.
I have good digital equipment and skills in photography, but am unable to capture the true color and fire of gemstones & jewelry. What is the secret?...Gaylene, USA.
I thank you for the implied compliment on my photos. I wish I had the secret. I've tried many configurations over the years. Presently I use a Sony Mavica digital camera with an attached macro lens. I shoot against a photo-grey neutral background with three 100W GE Reveal lights: one overhead, and one from each side. I diffuse the lights with cheesecloth. I do not use a tripod although I should -- I just shoot several shots of each gem, and almost always (by luck) one is in pretty sharp focus. I edit the images for color in Photoshop by using the "color cast" instruction -- that's why I use the photo-grey background -- PS looks at the image with the pointer on the grey background, and it "says" this background is not neutral grey but slightly reddish, so it automatically subtracts that much reddish cast from the whole image including the gem --> giving me near perfect color correction in one click. I couldn't get along without it. That's all I know and it's not much.
I recently purchased a ring containing a lovely 7.44 carat Russian demantoid garnet. Upon inspection, a local jeweler informed me that the stone had "horsetail inclusions". Could you elaborate upon this aspect of the stone, and provide some general information about demantoid garnets....Joseph, USA.
What you have is a true treasure. The horsetail inclusions are a definitive sign of Russian origin for the stone -- and that is the top of the line, like Colombia for an emerald or Burma for a ruby.
The size is enormous -- anything over 1 carat goes at a premium price. As far as information on dematoids in general, I'm sure you know their prestigious place in jewelry history, and the fact that until recently the Russian mines were no longer being worked. They are part of the andradite species within the garnet group and as such are distinguished by being a little softer, but far more brilliant and dispersive than other garnets. Their polish luster can approach "adamantine" (diamond-like) which along with their dispersion gives them the name "demantoid".
I am giving you two links where you can read up on the meaning and significance of your horsetails: the first is rather long -- it's a lesson in my gemology course on inclusions and using the microscope, so just scroll down to the appropriate part which is close to the beginning. The second is an essay on Included Quartzes which does mention demantoids and their special, value raising inclusions.
I have received from my mom a ring she had been given by her late husband. I have no idea where he got it, nor does she, he came home one night and gave it to her. She wore it constantly for approximately 30 years, it's in a tiffany-type setting. the stone itself is a round cut, 10 mm across. She had thought at first that it was an amethyst, since in daylight it is a rich violet color, however, in incandescent light, it turns a really striking hot pink. I know that there are pink tourmalines which can show a color shift, and I know that there are color change sapphires, which as their name implies, will change color with changes in light sources. From what I've recently read, it could appear that this might be 'alexandrium', which is a treated glass, and therefore - garbage. However, it was worn constantly, for 30 years, and there is no surface scratching, which I would have thought would occur with glass. I guess what i'm looking for is some reassurance that this might actually be worth owning, and possibly resetting, since the setting, itself is UGLY, while it's in 14Kt gold, the prongs are wide, and it's not pretty. I'd like to have it reset, but not if it's garbage. If it is, then I'll break the ring down and sell the gold and small diamond side stones...Cathryn, New York
Your gem does sound like Alexandrium, but it is not glass -- that was a trade name for synthetic color change sapphire, which explains its hardness and toughness. It was very popular about 40 years ago when it first hit the market and for some time thereafter. I understand what you are asking, but whether a piece is valuable to you or "garbage" is very much of an individual value judgment. If you think the stone is pretty and like the color change feature, you might want to keep it and have it reset, especially if it is something your mother valued and passed on to you. Most jeweler's will give you credit for the gold in a setting that they melt down to make a new one, which would hold the cost down. But, in truth, as a gem, Alexandrium it is not worth very much in the "marketplace".
I have been blessed to work at the Matilda Pfeiffer Museum in Piggott, Arkansas. One of the attractions here is the personal mineral collection of over 1400 specimens. I am not a mineralologist or gemologist. I am learning about them everyday though. One of the projects we are working on is to assemble a calendar for 2008. Last year's calendar was photos of the grounds and wildlife here. This year I would love to make the calendar using the birthstone minerals. We will use photos of the rough mineral specimens from Mrs. Pfeiffer's collection. My question is what mineral from the garnet group is actually used as the January birthstone? Is is a particular variety of andradite or grossular? The jewelry industry seems to use whatever terminology sounds best and not necessarily the correct mineral terms. The marcasite jewelry, is it really marcasite or is it pyrite? From what I have read marcasite isn't really stable, is that correct?...Teresa, Arkansas
Thanks for visiting my site. Your question is interesting. It sounds like you have a wonderful job -- what beauty you see daily!
The birthstones, as we consider them today, are actually an arbitrary group assembled from a mix of tradition and marketing needs. (For example the addition of citrine to November as precious topaz became less familiar than blue, and the addition of Tanzanite to December were market driven and of recent origin).
January: garnet, is pretty traditional and hasn't been "messed with" by the addition of alternate groups, except that now rather than the traditional pyrope and almandine choices, people are encouraged to substitute spessartine or grossular (especially Tsavorite) if the red-brown color of traditional "garnets" do not please them. So, basically, there is no officially sanctioned list and you can pretty much use whatever you think makes the most beautiful or interesting photos. I hope this doesn't throw cold water on your project, because it sounds like fun.
Here's a link to some photos and information on birthstones that I prepared for my students: http://www.acstones.com/birthstone.asp
As far as your quesiton on marcasite, you are correct that what is invariably called marcasite in jewelry is in fact pyrite which is more available and more stable than marcasite. Here's a link to an essay I wrote on pyrite as a gem that you might find interesting.
I just love smokey Topaz and Quartz. How do you tell the difference, and which one is better/more valuable/stronger??...Rochelle, USA
Actually there is no smokey "topaz", what is sometimes called that, is just plain old smokey quartz. This misnomer has persisted over the years despite the gem community's efforts to correct it. True topaz is harder but more easily cleavable and generally more valuable than quartz -- some smokey quartz is naturally colored, but most is produced from colorless quartz by irradiation processes. It is a modestly priced gemstone, but beautiful nonetheless.
I am currently enrolled in GIAs GG distant education course, and I've been doing research on gem identification tools/kits. Of course I started with GIA ($$$$)! I am leaning toward ordering from pretty rock.com however, I am treading in uncharted waters as I know nothing about good, best or better equipment.
I might add that I am not in the jewelry business, I enrolled in the course due to my love of gemstones. Any help you can provide will be greatly appreciated....Sharon, Nevada
I'm not sure from your email what equipment you already have so I'll just run down my own"essentials" list. You certainly don't need all these items right away, but taken collectively, they can just about solve any gem identification task. (The exception being those which require high-tech lab equipment.)
10X Darkfield Loupe (I use GIA's model daily): this is my work horse for day to day grading and ID
Gem Microscope with immersion cell (I use a B & L GIA Model)
Refractometer -- I have GIA's but I've heard good things about the one sold through Pretty Rock and I know the owners who are honest folks, who give good service and have excellent prices.
Polariscope -- again I usually use GIAs desk model, but I also have the mini one that fits over a mag lite from Pretty Rock and it comes in handy at shows.
Specific Gravity Hydrostatic Weighing set up -- this was purchased from Mineralab.com -- so much more precise than heavy liquids, this often makes the difference between something I can and can't identify.
I do not use a spectroscope -- just never got the hang of it.
I also recommend: Gemology Tools a comprehensive Gem ID computer program from Bill Wise. www.gemologytools.com
In the early 90's I saw a unique ring in Vogue magazine. It was an amethyst. The ring was unique because the stone was the whole ring. It was probably an 3/4 inch wide and about 1/4 inch thick. I have looked online for similar rings, but I do not know what to call something like that. I have seen onyx bands, but this was much wider. I would love one in garnet, but it is probably too soft. Please let me know what this kind of ring would be called...Kasey, Texas.
That kind of thing is technically called a "hololith" --- because of how tough they are, these items are usually made of aggregate minerals like jade, chalcedony or jasper. Band rings, bangles and interlocking rings are all in this category.
It's not the hardness (resistance to scratching) of a gem that's so important for this use, it's the toughness (resistance to breaking) -- and neither garnet nor amethyst are really tough enough.
Respected madam, I want to learn gemology online because I don't have that much money to pay, so please help me. Whether I can learn free online course of gemology in that way, or that will help me in making my career? Please suggest me...Nisha, India
You are welcome to take my free online course (www.bwsmigel.info) -- the only cost to you (and it is optional) would be purchasing the two recommended books. It will give you an entry level scientific understanding of the field of gemology, which would be of practical help to you in a successful future career in the field. However, you will not receive any credential or diploma from my class. Such credentials are often necessary in the business world. There are two other online gemology courses/programs (each of which has a relatively small fee compared to the big schools) that do give certificates: The International Gem Society (www.gemsociety.org) and the The International School of Gemology (www.schoolofgemology.com). Neither of these is as well known nor their credentials as widely recognized as those from GIA in the USA, or Gem A in Great Britian, but those schools are VERY expensive. I can personally vouch for the rigor and comprehensiveness of IGS and ISG as I have taken courses from both, and found them to be first rate.
I notice on Ebay that many gemstone pieces are described as 'authentic'. Is that an official term, and if so, what does it mean?...Margie, USA
There is no legally accepted meaning for the term "authentic" as used in describing gems or jewelry, although it implies not fake. The Federal Communications Commission (FCC) does not speak to that term, nor "genuine", although it does set the parameters for the use of the word "natural". My pet peeve word for gems and jewelry advertising is "real" (As opposed to what? Imaginary?).
I have found a cone shaped,clear, smooth, deep green heavy stone[for its size], which is about 3"by 2.5" at the base and narrows to about 1" at top .It is opaque without any air bubbles. Could this be volcanic glass or a green garnet? It is still rough, and there is no gemology lab nearby . I'm in The Rift valley Kenya where Tsavorites /green garnets are mined albeit at the coast...Peter, Kenya.
I'm afraid that without a picture or a sample of material there is little I can tell you. Do you see angular features like crystal face etching on it, or is it totally smooth? Have you examined it microscopically or at least at 10x for interior bubbles? It could be glass (although natural glass is rarely deep green), ceramic, tourmaline or a number of other materials. Perhaps it would be worth your while to send it to a lab for examination.
(Follow-up from Peter):
Hi Barbara, Wow that was fast! thanks for giving me those useful leads, I'll try and get a microscope and examine this piece though if I may ask, What is 10x on the microscope?  And if the stone I have is very smooth is it glass?  How would a gemstone react when subjected to heat of approximately 120 degrees? Because that's what I did with smaller pieces of the same material and I observed that it turned red hot but on cooling it still had its green color [the smaller pieces are about 5mm x 3mm x2mm and are a yellowish green ] and they didn't break . Sorry about the many questions it's not very easy to get a gemology lab around here though I've booked a session with a local lab to use their microscope. Lastly I've noticed some slightly visible linear curves on the material that look like they're not on the inside . Thank you in advance. Regards, Peter
Hello again, Peter:
The curved lines sound like conchoidal fracture marks which are typical of both natural and man-made glass as well as many gemstones. 10x means a magnification of 10 times larger than real life. If you have a 10x loupe you can use that instead of a microscope. Although angular markings are signs of natural origins, their absense tells nothing, as rounding can occur by alluvial action or even wind abrasion, or by human fashioning (molding, polishing).
I do not know about the color change on heating -- 120 degrees (either C or F) is not very hot, that is strange -- could be a luminescent effect. One more point -- if the material is opaque it would have relatively low gem value even if it turned out to be tourmaline, garnet, obsidian or some other natural stone.
When faceting a gem, how does one know, as one goes round the gem making facets, that one will have enough space left over to make the last facet? For example, if you start faceting at 12 o'clock, and make a facet for each "hour", isn't it likely that as you make the last facet (11 to 12 o'clock) you find that there isn't enough room (or, on the other hand, too much room) left in order to make the last facet exactly the same size as the others--in other words you run out of gem material (or have gem material left over)? With a perfectly circular gem I understand that this might not be a problem, since one can calculate angles, and the size of each facet. However, most gems are not perfectly circular...Christoper, USA
I'll answer your question first as it applies to modern "custom" faceting, and follow up with a comment on traditional, so-called, "native" cutting.
Faceting machines control three things for the cutter: depth of cut, angle of cut, and radial placement of facets. The modern highly engineered machine uses a selection of "index" gears with precisely spaced teeth. Let's say your goal is to put 12 equal sized facets around the perimeter of the stone (a round) -- if the gear has 96 teeth then you cut a facet every eighth tooth, and they automatically end up equal (that is if the cutter gone to the same depth, and the angle set on the machine hasn't been changed). If the outline is not round, perhaps oval or pear shaped, then the same twelve index settings would be used, but each facet would have to be cut to a slightly different depth and/or angle to make them meet up (the cutter is watching the process under magnification and much of it is "look, cut a little, look some more, cut a little," etc. Faceting diagrams are generally used, and they give a "cookbook" plan for the order and cutting sequence of facets in regards to both angle and depth that serves as a guide to the cutter.
Native cutters, on the other hand, who use just a grinding wheel, or even a simple jamb peg machine, have to do much more complicated calculating and visualizing in their head in order to make things come out right, and the resulting facets are almost never perfectly symmetrical, some will be smaller or larger, and they usually do not "meet" precisely. Nonetheless, my hat is off to them as it takes years of practice, and lots of talent, to be able to do a good job of cutting that way, whereas most people with a little dedication and training can do a good job with a modern machine.
If you'd like to see some pictures of what I'm trying to describe, go to my free gemology course, Lesson 7 "Gem Fashioning" and scroll down to the section on faceting: there are pictures of index gears and faceting machines, etc.
Here's a link: http://www.bwsmigel.info/Lesson7/DE.Gem.Fashioning.html
I've recently purchased a peridot ring set in sterling silver, and I am curious to know if the stone is a real one or merely a fake like crystal. Is there any 'testing' I can carry out, or clues that will tell me one way or another?...Tammy, Vancouver, BC
If you have a good 10x magnifier you could look for visible signs of natural peridot. Crystalline inclusions (angular, with high relief), would be reassuring as most natural peridots have some internal material. You also could look through the table at various angles and examine the rear facet edges with your magnifier to see if you observed any "facet doubling" (where the back facet edge looks like two close lines rather than one single one) -- peridot is highly birefringent, and often shows this characteristic, especially at some angles and in larger stones. One the other hand, bubbles (rounded high relief inclusions) and swirls, are signs of glass (crystal). Glass would never show facet doubling.
I have a ruby ring that is over 60 yrs old. How do I tell if the ruby is real?..Angela, USA
You are right to consider the possibility of a synthetic or simulant. Many people simply assume that synthetics are a product of modern technology, and that a piece with any age on it is sure to be of natural origin. Synthetic rubies have been in commerce since about 1900. A ruby of that age, if synthetic, would have been made by the flame fusion process. In good magnification and diffused light, you may be able to see either curved growth lines (striae) or bubbles, either of which would indicate synthetic. Angular or fingerprint inclusions on the other hand wouldn't be seen in this type of in synthetic, and are indicative of natural. There is also the possibility that the gem could be glass or some other simulant other than a ruby of any kind. Take the piece to a jeweler/gemologist for a professional opinion.
How can you tell the difference between Paraiba and apatite? I purchased a pair of earings from Brazil (1 ct ) the color is pool blue. When looking at the stone directly, you see a middle of translucent almost non-color. When looking upside down there is a non-color, but from a side or angle you have the blue of a Paraiba?? Deborah, USA.
By Paraiba I assume you mean naturally colored tourmaline that contains copper (the original specimens of which came from Brazil) -- apatite, also a natural gem, does come in a color similar to that of the Brazilian Paraiba stones, but is a quite different mineral. Notably it has lower refractive index, luster, and is much softer and more fragile.
From your description it sounds like you could have a doublet or a coated stone. It is also possible the stone is highly pleochroic, or badly color zoned. Unfortunately without seeing the stone in person and doing some observations and tests, there is little else I can tell you. Your best bet is to take it to a jeweler with some gemological training, who can evaluate the piece under magnification and/or do a refractive index test.
I am currently taking a correspondence course from the University of Wisconsin. It is actually a course in physics, and presently we are dealing with the difference between reflected light and refracted light. I am also studying your on-line gemology class. One of the areas I am most interested in is the section in your gem course dealing with darkfield microscopy. I have several stones that I found in North Carolina that under a 60 power microscope are flawless. Unfortunately, they are a 10 on the tone and saturation scales. I have talked to many facetors about how to cut a stone that is so dark, it does not show up well. Do you have any ideas? Love to hear from you, thanks, Mike...USA.
A stone with a tone of 10 is one which looks black under all normal lighting conditions -- some color may show when the piece is illuminated from behind with a strong light. Saturation, by the way, is not graded on a 0 - 10 scale like tone, and doesn't refer to how light or dark the hue, instead it describes the "purity" of the hue. By definition white, grey and black stones have no saturation.
I hate to sound discouraging, but there is no way to cut a transparent stone of tone 10 to lighten it sufficiently to result in a brilliant faceted gem. It should simply be cut like a cabochon as one would cut a black onyx or turquoise, alternately you could slice it very thin and cut tablets with faceted edges. Sad to say my reject box is full of pieces of facet rough that are clean, but just too dark to yield a brilliant stone.
(Follow up from Mike)
Thank you for the information. This is pretty much what I have been told by Phil Stonebrook. He is a member of our facetors' guild. I do not know if you know of him but he won the Masters 2 years ago. He said basically that stones that dark are usually a waste of time. However he is working on something that he thinks??? might help. He believes if you make the stone as shallow as possible without going below the critical angle and giving it a larger table than normal with a larger girdle this may allow a greater play of light inside the stone. So far I have not heard back from him but I will keep you posted. Again, thanks, Mike
Hello again, Mike:
Perhaps that would work with a stone that is a little too dark -- but as you describe yours, it sounds beyond that kind of help. When very dark almandite garnets were popular in jewelry in the late 1800's and early 1900's, cabs cut from it were often hollowed out on the back to let it light -- maybe you could do a cab this way and the thin shell over the concaved back would show color. It would take a lot of skill and be very hard work though.
Which is better a ruby ring or an opal ring? Which is the better stone? Which costs more?...Bonnie, USA
Hello Bonnie: You ask a very difficult question of which the first part can be answered very simply: better for what type of ring use? Ruby is much more durable than opal so for every day use ruby would be the better choice. Opal can be used in a ring as long as it is worn with care and only on occasion. Which costs more is much harder to answer, because "it depends" both rubies and opals come in a quality/cost range from a few dollars/carat for low grade material to specimens of museum quality which might go for $10,000/ct or more. Ruby is usually considered to be the most expensive colored stone -- but that is only for top specimens, and there are some black opals which come very close to top ruby per carat prices.
Thank you for your reply. I recently purchased an opal ring for around $300.00. I was concerned about getting one because I've heard they are a soft stone and easy to damage. I wanted to wear the ring not just have it sit in the jewlery box. I've been told to clean it once a month with oil. What are your recommendations on caring for the stone?...Bonnie, USA (follow up question).
Hello again, Bonnie:
A lot depends on whether you have a solid opal or a doublet or triplet, and how it is set (bezels are more protective than prongs). Doublets have a firm non-opal base and are somewhat stronger than most solids, triplets have both a firm base and a scratch and chip resistant colorless top and can usually be worn daily without fear. Assuming you have a delicate, solid opal, I still say: by all means wear your opal, but not 24/7/365. Wear it for the day then put it in the jewelry box, and wear something else for a day or two, then go back. Always remove the ring or wear gloves if you are using any harsh chemicals or doing hard physical labor.
Under no circumstances should you put oil on your opal. Opal is porous and the oil will seep into its tiny pores and oxidize and turn yellow over time. Simply use diluted dishwashing detergent and lukewarm water with a soft brush, then dry with a non-abrasive cloth and your opal will shine.
Hi, I am new to the "gem world", and would like to know what "AB Quality" means. Any help would be appreciated...Jennifer, Oregon
Unfortunately there are no set terms for gem "quality" as far as colored stones are concerned. There IS a rigorous and well defined system for grading diamonds that is near universal (GIA's). In that system diamonds are graded according to color, clarity and cut -- but that system does not use the term AB. Colored stones are also often quality graded by GIA, however the standards are less exacting and more flexible -- again no AB. I think what you have is some dealer or individual who is using their own, or a locally known system. You would have to ask them to define what they mean by that label.
If they are not following any of the major systems used (GIA, EGL, AGTA), etc. then they may be just making up whatever words they want. Just speculating: possibly in their "system" A is the best, B is only good, so an AB would be not as good as A, but better than a B. The trouble here is that we have no externally recognized criteria to use -- it's just their opinion right or wrong.
Dear Barbara (Barry), (This question is being answered by a guest expert, Barry Bridgestock)
I have a 6.5 mm gemstone and would like to have it set in a ring soon. I have read that "half sizes" are not available in snap-tite ring castings, so I think a 6.5mm gemstone would fit in a 6mm snap-tite casting. But, when it comes to setting it in, for example, a diamond semi-mount, what size should the gemstone setting be?? Would a 6.5mm stone fit a 6mm or 7mm setting and be secure, or would it be wiser to find a 6.5mm setting?
Also, could you please explain the difference between color shift and color change in gemstones? When it comes to color change garnets, is the change similar to Alexandrite, for example: I have seen on the gem TV shows Alexandrite that has a 90% color change, or is the color change more noticeable in the color change garnet? I have myself confused now, surely imagine I've confused you as well ...Jan, USA.
Mountings for 6.5 rounds are available from Tripps, Rio Grande and Stuller. To order from Stuller you have to be in the jewelry trade and have a resale number. Tripps and Rio Grande both have online catalogs at www.tripps.com, and www.riogrande.com. If you only have a choice between a 6.0 and a 7.0, the 7.0 is your best bet. Quite often the 7.0 mounting will be just a bit smaller than a true 7.0 due to shrinkage.
According to an article on color change garnets in Gems & Gemology (Winter, 1984), color change occurs with different TYPES of lighting, such as regular incandescent light bulbs vs. natural or fluorescent lighting. Color shift occurs when a stone's appearance changes because of the AMOUNT of light involved. Don't feel bad about being confused about this. It took me a long time last year to finally find definitions for these terms.
Some very rare color change garnets cango from blue to pink, but most color change garnets don't have the radical color change of a top quality Alexandrite. An Alexandrite with a change from a pure green to a pure red would have what would be termed a 100% color change because they are opposite each other on the color wheel (that's my theory, anyway). For garnets, a change from pink to gold or tan to pink is more typical. I did see one garnet rough for sale several years ago that went from a rich blue to red. It was priced at $450/ct. in the rough! I've also seen quite a few Alexandrites that went from ugly to uglier. (Kindly answered by master cutter and color change garnet fancier, Barry Bridgestock)
Hi. I have a gorgeous 5.75 carat cz that looks absolutely real. It is set in sterling and although it looks great, I hate the fact of having to clean the silver and I am thinking of taking the stone out and placing it with a 14 carat white gold setting. I know that cz's are not valuable. I would like to know if it's worth doing so, and if a 5.75 carat cz is the same as a real diamond equivalent? I was thinking of purchasing a real 5 carat diamond but looking at the prices at various jewelry stores one would have to hit the lottery to afford such a ring. Should I go to a jeweler and buy a good setting to give it an even more real appearance? Also, will my cz change even if it's in a gorgeous expensive setting in time? How long does it take for a cz to lose luster? I wear it daily...Diane, USA.
You are correct in recognizing that CZ has no intrinsic value, (the rough costs about 5 cents a carat), but that doesn't mean it isn't beautiful. If you love the stone and hate dealing with the frequent tarnishing of silver, I say by all means put it in a new setting. You could use white gold, or some of the newer sterling silver alloys which are virtually tarnish free, and much less expensive than gold. Ask your jeweler about them.
CZ is 8.5 on the hardness scale which is considerably softer than diamond, and a little softer than sapphire but a lot harder than most gems. How long it will look good depends on how rough you are with it -- but if you are relatively careful with it, it should last a long, long time.
CZ's are heavier per unit than are diamonds, but most sellers don't go by the actual weight of the CZ, they go by the "diamond equivalent" weight, so my guess is that your CZ is the same size as a diamond of that carat weight but actually weighs more.
Thank you for posting your gemology course and the general gemstone information on your site. I've read tons of information on demantoid garnet, some of which states that the darker green material is more valuable but less dispersive. What I would like to know is when it comes to hue, tone, and saturation according to GIA, which of the two is more valuable: a green to slightly yellowish-green hue, dark tone, strong saturation yG 7/4 SI-2 or a green to slightly yellowish-green hue, medium tone, strong saturation yG 4-5/4 SI-1??
The color of the first stone resembles a Tsavorite, and the second stone is the color of a Colombian emerald with medium tone and moderately strong saturation....Jan, UK
Thanks for visiting my sites and for you kind compliment. You pose a question that I cannot fully answer, however. I am not trained in appraising, and even if I were, I believe demantoids fall into that category of rare collector pieces for which there is no firmly set scale of value.
In general terms, however dark tone a negative factor. Whatever their actual color, dark stones tend to look black in poor lighting. Medium dark is ideal -- one of your stones is lighter than that, and the other is darker, so neither has the best color. As far as color trumping dispersion, again, I think one cannot say for sure. Certainly a light or overly yellow stone would be lower valued even if it had high dispersion, but a darker one, completely lacking in this property would also be less desirable than a slightly lighter one with it.
Although colored stones are not generally clarity graded by using SI (which is diamond terminology), I take it to mean that the first stone is visibly included while the second is eyeclean. Here, the nature of the inclusion would matter a great deal: horsetails are OK if visible, anything else would hurt value, and the horsetails are better when they are seen only with a loupe.
To sum up: I think a top quality demantoid would have Russian provenance, be close to pure spectral green (almost no yellow), medium dark, with at least some dispersion visible in good light, and with clear horsetails visible at 10x but otherwise eyeclean.
I recently read that most blue Topazes are irradiated to produce the blue colour. I have a light blue rectangle cut yellow gold ring (with two tiny diamonds set into the band) that was purchased in Rio de Janiero, Brasil in 2003. I'm now overly worried my ring could be radioactive, or was back then. I did not speak Portuguese at the time but my BF (now husband) does and I don't ever remember the person at the jewelry store mentioning the stone being irradiated. I've had the ring repaired once (the stone was loose), resized (after losing 45 lbs) and cleaned repeatedly.
My question is, how stringent are the Brasilian regulations regarding the sale of irradiated gemstones? Do I need to worry that my topaz might not have "cooled off" long enough before it was sold to me?...Lalania, ?
No worries at all. The regulations regarding holding times are carefully adhered to and double checked all around the world. There are different times of and types of radiation used to produce the different blue shades: London Blue requires a substantial cooling period, sky blue (your color), hardly any at all.
Enjoy your ring, you get far more radiation exposure from the sky and the rocks of the Earth's crust (called "background radiation") than from your topaz. :-)
I am looking at a 3 carat round brilliant cut diamond solitaire. It seems very clear and sparkly. The color looks like L or M. I can seewhat look like a few feathers and a little carbon around the upper edge with a loupe. The main thing is that when I look down the middleof it - with the 10 X loupe - I can see what looks to be a circle around the perimeter of the pavilion that looks burnt or something. It looks sort of like a hole. What could that be? I turned it upside down to make sure that the tip was still on the bottom of the diamond and it was. Also, when I held a white cloth behind the diamond., I could see the white color of the cloth through the diamond...Jena, USA.
Since you say the culet (point) is still there, what comes to mind immediately is that your diamond could be either horribly badly cut so that it has a large "window" (very unlikely) or that it is doublet with a diamond top glued or fused to glass or some material with a low refractive index. It could even be completely glass or some other type of diamond simulant. No way would a good diamond have a "read-through" effect such that you could see cloth behind it. My advice would be to go to a reputable jeweler and have them use their "diamond tester" on it. Make sure they test the crown, and the bottom at several places to rule out a doublet. If they verify it as a diamond, you might also ask them about getting it recut to eliminate the window.
What is hessonite garnet and how valuable is the stone?...Pam
Hessonite is a variety name for brownish orange grossular garnets which get their color from manganese and iron and it is sometimes called "cinnamon stone". Grossulars as a species come in a wide range of color varieties from the rare colorless form to yellow, the orangey hessonites, and through shades of light to dark green to black. The most valuable type of grossular is Tsavorite which is medium dark to dark green. Hessonites are relatively low on the value scale. They have characteristic swirly/bubbly inclusions (known as treacle) which make the overall appearance of most pieces a little sleepy. They make relatively good jewelry stones with good toughness and a hardness of 7.25.
Depending on the depth of color, clarity and size somewhere between $20 to $100 per carat might be a reasonable price, compared to fine Tsavorites which might fetch $1000 per carat.
I got a pair of earrings and I would like to know if they are genuine Moissanite. Is there any place in Las Vegas Nv. that I can get an appraisal? Thank You Patricia...Las Vegas
Only one company makes the diamond simulant Moissanite: Charles and Covard, so if you see their logo that is a good sign. Any competent jeweler should be able to tell you, as Moissanite passes the thermal conductivity test for diamond simulants, but fails the electrical conductivity test. Jewelers and even pawn shops, regardless of the city you live in have the tools to do these tests, but here in Vegas, try John Fish, Christensen's, Huntington's, etc....
I have a question about green amethysts vs. green quartz. I see both out in the marketplace. What is the difference? Is an amethyst part of the quartz family? Are they one and the same?...Stephanie, USA
There is no such thing as green amethyst: gemologically amethyst is defined as purple quartz.
Quartz is a gem species encompassing a number of quite different looking gems: amethyst, citrine, rose quartz, rock crystal, chalcedony, agate, jasper, aventurine, tiger'seye, etc. All of these have the chemical formula SiO2 and the structural pattern inside the crystal referred to as trigonal, and share many optical and physical properties. They differ in outward appearance because of trace elements or inclusions present. or because of the size and pattern of the individual crystals making up the gem.
When most amethyst is heated to a certain temperature, the purple turns to gold/orange and you get citrine, but some amethyst with unusual trace chemistry turns green. Such stones are referred to as "greened amethyst" referring to the heat induced change. Nature sometimes provides the heat, so in rare cases this green quartz called prasiolite is found naturally.
Some types of colorless rock crystal quartz can be irradiated to a greenish yellow color and have been given the trade name "oro verde" quartz.
I recently bought a Tanzanite stone on ebay from "-----------"...he has a 1500 rating with 100% positive feedback....well it is a gorgeous stone...I then brought it to a well known jewelry store, and had them send it away to their gemologist/jeweler to make it into a necklace for my girlfriend....I got a phone call telling me it was a fake....the guy has been working for this outfit for over 17 years and says he deals with all kinds of diamonds and gemstones and said when he saw it under the microscope, he could just tell...now the ebay dealer says he guarantees it's real....says he'd put aything on it that it's real.....so I'm stuck, I do not know who to believe....the dealer told me to take it to a reputable gemologist.....What should I do here?...Sean, USA
I'm sorry you had such a bad experience -- things like that make it so much harder for the rest of us internet merchants to do business. I do not know of any conclusive test that will identify "fake" Tanzanite, visually with a microscope, although there are other standard tests such as reading the refractive index, using a dicroscope, or doing a specific gravity test, that would be conclusive. There are some quite visually convincing simulants out there, but none of them pass the RI & SG and pleochroism tests as Tanzanite. See if you can get a written report from the jewelry store guy detailing what tests (if any) other than microscopic examination he did, and what the results were. If they won't provide that, then what you need is an official identification. AGTA, GIA, etc. provide that service -- I would ask the ebay dealer to send it to AGTA or GIA on your behalf for an ID. (The good news is that you'll know for sure what you have, the bad news is that it will cost about $75 - $100 and take several weeks).
I, as well as the bulk of the world, am fascinated by Diamonds. The hardest natural substance known to man, so brilliant, so much so-called "fire", HAS to be the most rare and valuable on Earth, right? That was a Rhetorical question by the way: for I know the answer. But really, what makes a Diamond SO FRIGGIN' EXPENSIVE??, when there are so many other gems so much more beautiful than a plain ol' diamond ( Yes diamond without a capitol D.) I feel that diamonds are over-rated just the same way as Ferarris and Lamborghinis. A Ferarri is beautiful in style and form just as a diamond is. But what about comparing an old Camaro with a Iolite? And then comparing the latter with diamond /Ferarri?! The difference, I think, is the "snob-effect". I love Ferarris, and diamonds. But, the stereotype clearly tells me that I probably will never own a Ferarri or an exquisite diamond until I have a casino on The Las Vegas Strip. I just wonder why diamonds are so expensive, so sought-after, when they are not really at all truely "rare" NOR are they the most beautiful gem of all the world. In my eyes anyways. Thanks for your time...Ryan, NV
All gems are rare and beautiful, in fact, that is part of the definition of a gem. As to the special status that is accorded to diamonds, there's no "one size fits all" answer.
Part of diamonds' appeal is the uniqueness of the luster/hardness/dispersion combination which no other natural gem can precisely match. Part is historical with romantic and legendary diamonds and diamond jewelry forming a part of our collective consciousness. A large part, in my opinion, is due to a carefully regulated market where demand is fueled by intensive and emotion laden advertising (think of the "a diamond is forever" & "the right hand ring" campaigns), and where supply is largely controlled by a single player.
The present diamond market is currently threatened by two main forces: the breakdown of the near monopoly on gem rough which no longer involves over 80% of the supply, and the introduction of difficult to detect synthetic diamonds. BTW, it's not the jewelers who are getting rich, as diamonds, many tell me, are one of their lowest profit items.
In 1983, I was given a tiger claw set in gold while I was staying in Guam. It has lived with me since in Arizona. I would like to start wearing it again. The claw has fallen out of the setting and seems quite dry. I did a google search for tiger claw and care info and found your wonderful website.
I wonder if you could just tell me how to care for this (should and can I buy keratin product for it? lanolin? Olive oil? Just wearing next to skin?) and also, would it do damage to the claw if I use something like Super Glue to set it back in the gold?
I didn't want to just take it to any old jeweler because of the unique and sacred properties of this item...Kathleen, AZ
If you've read my essay on unusual organics, I'm afraid you know pretty much all that I know about care of something as fragile as a tiger claw.
With the humidity so low in Arizona, I expect that is why the claw shrunken and come out of the setting. I wouldn't use super glue to reattach it, but rather 5 minute epoxy which would be more elastic and cushioning for the piece. When you aren't wearing it you should keep it either vacuum sealed in its box (if you have one of those vacuum food sealers) or alternately in a container with moth crystals -- these will protect it from dermestid beetles. Do not get it wet, as that would speed bacterial/fungal decomposition.
I don't recommend any oils as they no not hydrate and can cause discoloration, but the least likely to be harmful would be pure mineral oil. I think if it were mine I'd consider coating it with a light application of polyurethane lacquer (semi-gloss or matte), and I would wear it only rarely. Sadly, such items are ephemeral and all we can do is to try to prolong their limited existence as best we can.
Yesterday I purchased a pink sapphire lab created ring with, I think, 10 or 14K white gold. it was from *****'s Jewelers. It is a triangle and under it is 10 square shaped lab created sapphires on the band. There also are a few little diamonds on the side. Is $267.00 a good deal? Also I shouldn"t have any problems wearing this every day should I?... Kimberly, NC
I can answer one of your questions easily. Sapphire is very hard and very tough and makes a good companion stone to diamond in an everyday ring -- and white gold is noted for its strength as well. All you need to clean the stones is detergent and a toothbrush, and you can use a jewelry polishing cloth on the metal to keep it shiny. This piece should look beautiful for many years.
As far as whether you got a good deal, though, there are too many variables to give you a definite answer (for example, the karat level of the gold, its weight, the clarity and caratweight of the diamonds, etc.), and I have no direct training in doing appraisals. The lab sapphires have very little intrinsic value, so the "worth" of the piece would mostly be set by the gold and diamonds. Off the top of my head, it doesn't sound outrageous for a retail price at today's over $600/oz gold prices. I think you did OK. :-)
When cutting a Ruby gemstone, How can one determine the grain? assuming the rough is six sided and flat on both ends, are there any books covering reading the grain?..Jim, FL
Unlike diamond and especially kyanite, corundum does not have significant hardness differences in different crystal directions that can complicate cutting. Usually it's these hardness directions, requiring different strategies for successful cutting, that are referred to as the "grain" in gem cutting -- similar to the use in woodcutting. So I don't think you need to worry about it.
On the other hand, all corundum gems (sapphire and ruby) have pleochroism with a subtle but important color difference when viewed down the C axis as opposed to the A or B axis. Perhaps this is what you are referring to: Thinking of a pencil, the length and width are the A and B and the depth is the C axis. So as you are looking through those flat hex shaped ends you are seeing the C axis color. If you prefer that to the color you see when looking through the long sides (A/B) then use the flat side for your table and that color will predominate face up, otherwise orient the gem with the table towards the long side.
If you haven't yet read Glen and Martha Vargas' book "Faceting for Amateurs", it has some good material on orientation of rough.
A few years ago I purchased a number of lovely large pieces of Peruvian blue opal in Tucson. When I showed them to my friends at the rock shop, they almost fell over, and gasped at what beautiful chalcedony I had. So what, exactly, is Peruvian blue opal. Is it the same thing as chalcedony, and why did they react like that?...Gail, OR
Thanks for your question, it's a good one. Opal, whether with play of color (precious) or without (common)--like your Pervuian material, is made of ultra-microscopic spheres of a solidified gel-like form of silica (SiO2) called cristobalite. It is considered an amorphous material (without crystal organization) and has a hardness between 5 and 6 and poor toughness. Chalcedony (along with agate and jasper) are also forms of silica (SiO2), but in this case it is organized into microscopic quartz crystals intermeshed into a form known as an aggregate. Such gems have hardness of 7 and are very tough. To further explore the issue, amethyst, rose quartz, tiger'seye and rock crystal are also silica, but in this case, organized into macroscopic "single crystals", they have a hardness of 7, but are not as tough as their aggregate cousins. Chemically, then, these gems are all very similar, but the physical arrangement of their atoms is quite different, accounting for their different hardnesses, refractive indices, colors, transparency and phenomena.
Now, back to your friends' reactions. A very rare and expensive form of chalcedony that is colored blue to blue green by microscopic chrysocolla inclusions is called "chrysocolla chalcedony". Superficially, good blue opal looks a lot like it. Both are in the same color range, with similar translucence and the same glassy luster, but chalcedony is much harder and more durable than opal. Your friends, I think, mistook your blue opal (which is itself a relatively expensive gem) for the very expensive gem, chrysocolla chalcedony, which rarely comes in good quality pieces larger than 2 - 3 cts.
A diamond is crystalized carbon. What, then, is crystalized tin? Is it a rare colored stone? I found some in Bolivia and I can't find any information about it, can you please help me?...Carlos, Bolivia
Although carbon, gold, silver, sulfur, platinum and mercury do occur in a crystalized "pure" state, tin does not. Tin is always found in nature bonded to other elements, such as oxygen, sulfur, iron etc. The only gemstone I know of that contains tin is cassiterite which is tin oxide SnO2 and which does occur in Boliva. It is a rare collector stone, usually reddish brown, and has some value if it is transparent and free of inclusions. There is small demand for it, however. Other minerals such as stannite and cylindrite also contain tin but are not useful as gemstones.
Have you ever heard of a Namibian tourmaline, blue-green, called neuchwauben?...Peggy, USA
Neu Schwaben is the name of a particular mine in Namibia where beautiful blue-green colors have been found. So that term is just being used as a place name for where the tourmaline was mined. Several of the blue-green tourmalines that have been cut by Barry Bridgestock on my site, have come from that locale.
First of all, thank you for taking my question - just recently I inherited a ring and had it appraised by a local Graduate Gemologist, and wanted to run it by you. Her written appraisal was :
"Ladies custom designed 14-karat yellow gold fashion ring set with 1 blue topaz - in a 4 prong basket head.
length 24.69mm; width 19.95mm; depth 11.45mm
depth % 57.4
primary color: blue
secondary color: green
color intensity: medium
est. weight: 49.91 carat"
(I will leave out the ring stuff) it is stamped 14k and ACD
She appraised it at $1,400 (insurance value)
I am touched my grandmother has left this keepsake to me and just want to make sure I can afford to actually wear it. I was considering having it converted to a pendant; but want to preserve the ring setting also. Thank you for your time and expertise... Wendy, TX
I'm delighted to take your question. As per usual, of course, I cannot make any valid judgments about a stone I haven't seen and tested, but just let me make a couple of "off the top of my head" comments.
The appraisal looks like it was thoroughly and professionally done. Insurance value is always set on the high side due to the difficulty of sourcing a particular size, shape and setting for a piece of jewelry. Given that, the value seems like it's in the right ball park.
The one thing I would point out is that the appraisal fails to note whether the stone is enhanced (treated) or not. The term "natural" only applies to whether a stone is from Mother Earth or made in a lab (natural vs synthetic). Many natural stones are enhanced by various processes like dyeing, irradiating, heating, coating, etc. I am fairly sure that your blue topaz is irradiated. These were produced starting in the early 70's from natural white topaz which is available in large, clean pieces. Unenhanced blue topazes do exist, but they are rare, generally pale and rather small, and a 49 ct. one would be worth much much more than the value given to your ring.
Without enhancements we wouldn't have Tanzanite, or black onyx or several other well known and loved gems, so saying your topaz is enhanced is not to run it down. In my opinion, however, the appraisal should have indicated the gem's enhancement status.
Your thought about converting it to a pendant would be wise if you want to wear it frequently, as topaz although hard, is fragile, due to its tendency to cleave. A good custom jeweler should be able to dismount the gem, remake the ring setting into a pendant and remount it for you -- keeping the character of the setting virtually the same. Congratulations on receiving this beautiful piece with both monetary and sentimental value.
I am interested in pursuing a career in gemology, but I want to get some information about this field before spending the time and money. I would be very grateful to you if you could shed some light on this subject. I am 40 years old. I have a graduate degree from India in Business. I have worked as a school administrator in India. I owned my own skin care business here in the US. I would like to change my field as I am no longer enjoying what I do. I have always been fascinated with gemstones. As India is a land known for its gemstones and diamond cutting, I want to get into this field.
I would like to do a course in Gemology. Where is the best place that I can get good training and certification? Is GIA the best???? What are the job prospects like in this field? Please, please reply.... Sujatha, India.
Gemology is a growing and rewarding field, although it is one in which there is a lot of competition. First of all, do not let your age worry you -- I started my successful gemstone business ten years ago when I was 50. The fact that you have a degree in business along with your life experiences make you much more likely to succeed than a younger, less experienced person.
May I suggest that you start your examination of the field of gemology by taking a quick overall look at my free internet gemology course: http://www.bwsmigel.info This class will not lead to a credential or any employment opportunities, but will give you a full overview of the most important aspects of the field of gemology from a scientific, rather than a retail or artistic, viewpoint.
As far as schools there are many good ones, and these days on-line opportunities for instruction abound. The International Gem Society and the International School of Gemology both have inexpensive courses which lead to credentials -- however, the downside is that these worthy institutions do not yet have the world recognition of GIA or some of the more established schools.
Visit this link to Gemology on Line http://gemologyonline.com/Forum/phpBB2/index.php and note the comments comparing the world's three most well known credentialling gemology schools.
I have found your site very helpful. I wonder if you could give me some advice regarding emeralds. I am very drawn to this stone and would love to purchase an emerald ring, however several people have told me that emeralds are fragile, and not suitable as an engagement ring. Is this true? ....Pam, UK
The fragility of emeralds depends a lot on how included they are. A specimen with no fractures inside (rare) would have the beryl family's hardness of 7.5 - 8 and be relatively tough. Most emeralds, though, have some internal fractures which are then filled with oil to make them less vivisble. This diminishes the toughness somewhat, and decreases their stability to temperature and solvents. So, the folks who are giving you advice are, unfortunately, correct that emerald is not a good choice for a 24/7/365 ring. I know of no bright green gemstone tough enough for that application. :-( Use emerald in occasional rings or a daily wear pendant or earrings only. The best colored stone choice for an engagement ring is sapphire (tough and with hardness 9) -- they don't really come in a vivid emerald-like green, but they are available in lots of other pretty colors.
I would like to know if it is possible to dye natural rock crystal quartz, and if so, how to do it so that the colors do not fade or wash off. I am interested in achieving fairly bright primary type colors....Lynn, USA.
The short answer to your question is that it cannot be done. See below for long explanation!
Unfortunately it is not possible to dye a clean piece of rock crystal quartz because it is an inpenetrable solid single crystal -- well, it IS possible, but only by first creating a myriad of tiny fractures in the quartz which destroy its clarity. Dye can only enter a monocrystalline material like quartz through cracks and fissures. This ancient process is called "quench crackling" and involves heating the quartz or other gem material to a high temperature, and then immediately dousing it with cold liquid. The resulting, fractured, porous material will then take up dye in its cracks which from a distance will give an overall appearance of color. In the pictures below you can see what a dyed quench crackled rock crystal pebble looks like, and how the color is actually only in the cracks.
You CAN successfully dye aggregate forms of quartz like agate, jasper and chalcedony, because they are NOT made of a single giant crystal, but instead of a multitude of submicroscopic crystals with micro-spaces between them, whereby dye can be taken up. Black onyx is an example of a dyed quartz aggregate.
It IS possible to change the color of rock crystal, in fact gem treaters do it all the time, by not by dyeing. They use combinations of irradiation or high temperature processing that change the internal chemistry of trace elements, or structural features in the crystal. This is how "Lemon quartz" is made from rock crystal, or colorless quartz is turned into smokey quartz.
Another color changing possibility is to coat the rock crystal with a paint or metallic vapor, but such coatings are very fragile, and the metallic ones create iridescent effects, and require high tech equipment. The picture below is of a vapor coated rock crystal quartz crystal, this material is sold under the tradename Aqua Aura Quartz.
Sorry to be the bearer of bad news.
Recently I took a diamond ring to a jeweler and he used something about the size of a little penlight and touched the end of it to my stone to determine if it was real or CZ. I believe if it's fake it doesn't make a sound, but if real, it emits a beep. What is this tool called and where could I purchase one? Approximately how much is one? Thank you much.....Lanette, USA
Generically known as "Diamond Testers", they are sold by jewelry supply houses like www.tripps.com or gemological instrument suppliers like www.prettyrock.com, and there are various trade names for the different brands. They cost @ $100 - $200. The older, less expensive, versions use a "thermal conductivity" test. That is, the device reads how well the stone conducts applied heat away -- diamonds read quite differently from their simulants, like glass, white spinel, white sapphire, YAG and CZ. These worked great until Moissanite was invented and introduced as a diamond simulant a few years ago. Moissanite will pass the old style test as diamond, so the newer models use both a thermal conductivity to separate diamond from CZ and other simulants, and then an electrical conductivity test to distinguish diamond which does not conduct, from Moissanite that does. Most of the models I've seen beep when the probe accidentally touches the metal of a setting. What these devices will NOT do is to identify a true synthetic diamond, or determine whether a natural diamond has been enhanced. Those discriminations require more expertise and additional equipment. Your jeweler probably has the newer version which is available from the same venues as the older thermal tester. Pawn shops couldn't stay in business without them! :-)
What is the difference between high zircon and low zircon? And what are the colors that low zircon comes in? And the colors for high zircon?....Diane, California
Before the modern days of gemology, miners and gem traders noticed that the luster, and other properties of various color zircons differed, sometimes dramatically. As it became possible to measure characteristics like refractive index, this observation was further supported. Among zircons, the great majority of stones have near adamantine luster when polished, and a refractive index so high (1.93 - 1.98) as to be "over the limits" of the standard refractometer (as is diamond). A few zircons, though, almost invariably those that are green, have a glassy luster and a lower refractive index. The term "low" (or metamict) zircon had long been in use for these, and "high" zircon for the more common type.
Zircon sometimes contains impurities of radioactive minerals -- over long periods of time, as these decay, the radiation damages the internal crystal structure of the zircon causing the gem's properties to change. In extreme cases, all crystalline structure is lost, resulting in a type of natural glass -- such stones no longer show the properties of crystalline zircons, so they are "low".
The majority of mined zircon rough occurs in a range of yellow brown to orangey brown colors. Most of the cut zircons on the market, especially the blues, whites, yellows and reds have been produced from these brownish ones by various heating processes.
Color in gemstones, in general, can be caused by the atoms of which they are made (either their own chemical formula -- or by trace levels of impurities). Heating often changes the chemical state of atoms from one ion to another, thereby changing color. A second attribute which causes color in gems is defects in the crystal lattice -- these can occur naturally as with the green metamict zircons, or be produced on purpose by irradiation, as in the case of color enhanced diamonds, and some other irradiated gems.
So, in a nutshell: low zircons are glassy and green due to natural crystal breakdown from radiation, all other colors are either natural, or produced by deliberate heating.
I've got a question which I hope you can enlighten me on. I came across "black rhodium" as a material used for rings on a website I visited. To see them, visit Perlini Silver and, under "Collections", click on "black". There are rings which are made of black rhodium.
However, when I tried to search on the net for such a material, there is almost no information about black rhodium. In fact the most I could find was regarding rhodium on Wikipedia which states that: "A rare silvery-white hard transition metal, rhodium is a member of the platinum group, is found in platinum ores and is used in alloys with platinum and as a catalyst. It is the most expensive precious metal."
Have you come across this material?....Ivan, Singapore
Yes, I have seen "black rhodium" used in some ring settings, especially in bezels around stones, and I took a look at the "black collection" at Perlini's website. Although I do not know for sure, but I expect it is a rhodium plating (the pure stuff would be very expensive), which is then treated to darken it. Perlini is a silver jewelry company, after all, and ordinary white rhodium is commonly used to plate sterling silver jewelry to prevent it from tarnishing.
Most metals can be given a colored patina by some sort of chemical or electro-chemical treatment. Examples are the dark "antiquing" of silver done with "liver of sulfur", and the electro-chemical process used to make a multicolored iridescent patina on titanium.
That would be my best guess. :-)
I am a new gemstone enthusiast and was recently searching on ebay and came across several very large, Asian based, gemstone companies selling enormous numbers of stones both on ebay and through their own huge websites. Can you make any general comments on these type of companies and their wares?....Susan, British Colombia
I am quite familiar with several of the companies you are referring to: here are my impressions based on the fact that I have been observing them, and interacting with them, and their customers, virtually since they opened up.
1) The ones that have stayed in business over the long term are a reputable firms.
2) Most have guarantees and return policies, so that you can get your money back if you don't like the goods. In some cases this process takes a pretty long time, in other cases they work through US return centers and are quick. A general rule that would apply not only to gems, but to any internet purchase is not to buy anything that you can't return.
3) For the most part they sell what would be termed native cut, and "commercial" cut gems. Most of these have some deficiency in shape, proportion, faceting meets or cutting angles which lead to a "window" (an area of non-brilliance in the center), an ungainly outline shape, a bellied pavilion, and/or a flat crown. Custom/precision cut gems are simply more expensive, regardless of whether you buy them in Thailand, the US, or Africa -- on the net, or at a show.
4) The colors of the gems that are offered are usually either light, dark, highly zoned, or lack saturation compared to higher value specimens of the same species. High color grade stones are simply more expensive, regardless of whether you buy them...., etc, etc.
5) The quality control departments of at least one of the biggest of these companies has had lapses that I know of (two different customers of mine, over the years, have sent me gems to identify for them which they purchased as one thing from this source, and which turned out, upon testing, to be something less valuable. This is understandable, though, in the large scale operation they run, and is very unlikely to be deliberate. Garnet and spinel, for example, overlap in color and luster, and without testing each one individually, errors can occur.
6) I believe most of the "surviving" sites have improved in recent years, but in the early days, customers often complained that they would see a "generic" picture, and the gem they actually got was similar to, but not the exact one in the photo. Personally, I find that some of the gem descriptions on these sites get to be comical after a while (all are "screaming" color or "blinding" brilliance, etc -- as if they have a "mix and match" set of adjectives, that their employes just grab and stick randomly in the boxes.)
7) Value-wise the gems are worth about what you are paying for them -- if you purchase a $50 ruby, you are not getting a great bargain on a $500 stone, you are getting a ruby worth $50. A listed "retail" price means little to nothing -- I could list retail prices of 5X-10X, or more, than I am charging for the stones on my site, and I'd be perfectly correct if these same stones were being sold, retail, at Tiffany's or on Rodeo Drive.
8) I do credit one of the largest of these companies for recently starting a campaign to educate their consumers - they have some really good essays, and pictures on their site, and an informative newsletter you can subscribe to. Also, they have been kind and generous to me, in letting me use images from their site for my gemology teaching.
If all of this sounds very negative, I don't mean it to, many of their items look pretty good once mounted, and are probably somewhat cheaper than you'd get for comparable goods in the US given labor costs, etc. And every once in a while they do come up with a pretty good stone for a very good price. I think, like most new collectors, you will go through a stage of wildly enthusiastic buying, but as you learn more about cut and color you will probably tend to buy less from such sources and concentrate on fewer but better cut and higher color grade stones. I have boxes of this type of lower quality gems that I bought in my own early collecting days. All of us do. It's almost a necessary growth process.
(For a set of related comments on TV shopping channels and their gems, you might scroll down on this "Ask Barbara" page to the very first question.)
I have a strand of Green Gold faceted pear topaz beads. Is this the same as Lemon topaz? My understanding is that the Green Gold topaz is more valuable than the so-called Lemon, however, now I'm wondering if they're just the same thing....Lauren, USA.
Unless you are talking about one of the new, yellow, diffusion colored topazes, with which I am not very familiar, I know of no "Lemon" topaz or "Green Gold" topaz. On the other hand, those terms are frequently used for irradiation induced colored forms of quartz.
As you are suspecting, I think there is no real difference between them, it's just a matter of what the seller wants to call them, in other words, both are trade names for enhanced quartz, neither of those terms is a valid gemological variety name.
If there is any value difference between either of these two forms of quartz, it is minor - both are worth only a bit more than the colorless quartz from which they are obtained.
My husband gave me a Tanzanite ring for my 60th birthday. The cut is a marquis. It has a beautiful blue/purple color. However, when I look at the stone from the bottom, it has no color! Is this normal? The ring was purchased from a reputable jewlry store....Terry, St. Louis, Missouri.
Yours is a very interesting question. I've thought about it a bit, and can see three possibilities. My usual disclaimer of not being able to make any definitive answer without seeing and testing the gem applies, however.
1) Many stones are colored unevenly (called color zoning). The color we see when we look at a faceted stone from the top may not be its color throughout. The facets cause light to bounce around inside the stone before it exits to your eye and tends to blend the differently colored areas of the stone into a single color. I have seen some pieces of rough that are very light, but when faceted skillfully, because there is a darker area right at the culet (pointed bottom) where most of the reflection occurs, they look much darker as cut stones. It is possible that your stone was highly color zoned and well cut to compensate for it. By turning the stone over you are minimizing reflections and color blending and color zoning would be more visible. I have seen this phenomenon most strongly in amethyst and citrine and also in sunstone and sapphire. I am not familiar with extreme color zoning occurring in Tanzanite, but it is possible.
2) Both Tanzanite and iolite are gems which look different colors from different angles (pleochroic). With Tanzanite the two colors are generally blue and purple. With iolite there are three: a blue-violet color (very similar to Tanzanite color) a grey blue, and a light straw yellow (near colorless). Tanzanite and iolite can sometimes be confused if they are not closely examined. Perhaps the stone is an iolite and when you turn it over and view the bottom you are looking at the near colorless axis.
3) One type of simulated or imitation gemstone is called a doublet. In a doublet the top and bottom of a gem are made of different materials. One of the characteristic features of some doublets is that the top is brightly colored and the bottom is colorless. When these are made to deceive they are generally put in closed settings so the back cannot be observed, but they can be found in prong settings as well.
My suggestion would be to take the ring back to the store where your husband got it and ask to speak to the jeweler or owner (not just a sales clerk). Show him/her the piece and explain your reservations about it -- you might also show them this note. Even if the stone is not what you expected it to be, it might be an honest mistake on their part. The people who supplied them, or those further back in the chain who supplied the supplier, may be at fault. A reputable firm will stand good for their product, no matter who was at fault.
If you end up keeping the ring, let me add that Tanzanite is not a highly durable ring stone. You should reserve the ring for occasional wear as this gem is rather soft and somewhat cleavable. If you want to wear it daily you might consider having the jeweler reset it as a pendant. BTW, I would be very curious to know what you find out from the jeweler.
I'm I able to test a blue chalcedony with a Jadeite Filter? If so what color should it be thru the filter? Secondly is a blue chalcedony Quartz?.. Jimmy, Canada
So far as I can determine, a jadeite filter will not detect dye in chalcedony -- it is specific to chromium and, in general, that would not be the dyeing agent. Although a great deal of chalcedony on today's market is dyed (especially in "sea foam" colors and darker blues), there's still a lot of natural around. One old fashioned, but often useful, method is to examine the surface of the stone under high magnification -- in some pieces dye will show up as concentrations of darker color in minute fissures and pits.
In addition to worrying about dye -- chalcedony can be simulated quite convincingly with glass, and recently I have seen some translucent cubic zircona cabochons that were a dead ringer for fine blue chalcedony!
Yes, chalcedony is a type of quartz. It has the same chemical formula (SiO2) and the same trigonal crystal structure as amethyst or any other quartz, but its crystals are ultra-microscopically small and randomly oriented. Such a material is referred to as an aggregate. So in a nutshell, chalcedony is an aggregate form of the mineral quartz (as are agate and jasper).
What's all this hoopla about imperial garnets? I see so many that are from Tanzania or from Madagascar. They all look different. What makes an imperial garnet? There seems to be some type of color shift or color change involved... Diane, California
So far as I know, there is no official variety "Imperial" garnet -- it's just a trade name with no defined meaning. It's a case of "romancing the stone".
To my knowledge there are only three recognized gems with Imperial as part of their variety names: Imperial topaz, Imperial jasper and Imperial jade -- even with these long established gem names, great liberties are taken by sellers who give lesser materials these names to justify prices.
With a trade name, just about anything goes. This is well and good -- it's free enterprise, capitalism, Mom, and apple pie, as long as the seller acknowledges that the name is made up.
I do this on my website by using a name in quotes: so if I call some unusual serpentine that has golden pyrite patches "Oro Verde" serpentine, or a piece of antique glass purpled by the sun, "Desert amethyst", the quotes are meant to make it clear that this is simply a descriptive or marketing term, not a taxonomic one.
In the case of "Imperial garnet" one seller may use it to designate a piece with a slight color shift, while another may use it to indicate a particularly vivid color of grossular or Spessartite.
I bought a turquoise/silver bracelet from a Native American woman at a jewelery table in Oregon and paid $100 for it - one year later, the turquoise color changed on part of the stone. It looked like it got wet and became discolored. I was frustrated and feel like I was conned. I forgot what mine she said it was from. Anyway, I took it upon myself and took the stone out of the bracelet and put in on my electric stove burner and the stone turned black, it burnt - was this the wax or was it a turquoise mixture - anyway it was a lesson for me not to throw money was like that again! Question: real or fake turquoise - I like turquoise but am reluctant to buy anymore. Thank you...Kim, USA.
I'm sorry you had such a bad experience with your turquoise jewelry, and all the questions and concerns you raise are reasonable.
Very often I have the unpleasant task of explaining to someone why they were "taken" when they bought something. Although I cannot say anything for sure without having seen and tested the turquoise, I think in your case the news may be good.
In general, turquoise is quite porous and it absorbs skin oils, lotions, sunscreens, household chemicals and even pollutants from the air. With time, this makes an often-worn piece change color, usually to a browner, darker tone. When turquoise has black or brown matrix running through it, those seams are places where absorption and differences in the density of turquoise patches occur. It would not be unusual for a piece of natural turquoise to do what you describe.
In fact, waxing the surface, as is usually done with fine "Persian Grade" turquoise helps to retard such absorption. So waxing is not necessarily a bad thing. Turquoise is also a heat sensitive stone, and will definitely darken or blacken at high temperature. I doubt your piece was plastic or resin as it would have smelled absolutely awful as it blackened.
There are many grades of natural turquoise some of which are more porous than others. Very porous types are usually "stabilized" with a plastic resin which is drawn into the pores with a vacuum. Such turquoise would still be considered of natural origin, but should be sold as "enhanced".
A synthetic form of turquoise is manufactured with and without matrix and is sold by some of the larger wholesalers that supply jewelers. (Even some Native American jewelers use it for less expensive pieces.)
Turquoise simulants such as pieces made of ground up turquoise with dye molded in epoxy, glass, and ceramic or plastic imitiations are also available on the market. If they are properly advertised they would be called "faux" turquoise, but too often they may be passed off as the real thing in which case they would qualify as fakes.
Here's a link to my essay on turquoise where you can see pictures and read a little more about it.
In the short run it is best to buy from established firms that offer a money-back guarantee.
What is the difference between beryl and chrysoberyl? And if there is a difference, why does chrysoberyl have the word beryl in it?...Diane, California
Beryl and chrysoberyl, although similar sounding, are two completely different minerals, the reason that "beryl" appears in both their names is due to the fact that the element beryllium is part of each of their chemical formulas. (There are other, lesser known beryllium containing gems such as phenakite, hambergite, taaffeite and tugtupite whose names do not so easily give away their elemental components).
What makes each of the world's minerals unique is the number and kind of atoms in its chemical formula, and how those atoms are arranged in its crystal structure. There are more than 3000 named minerals!
Beryls (varieties: emerald, aqua, Morganite, helidor, etc) are: Be3Al2(SiO2)3 -- chemically classed as "beryllium, aluminum silcates, and those atoms are put together according to the hexagonal crystal system building plan. They have a hardness of 7 (the color differences between the varieties are due to trace amounts of different elements such as chromium, vanadium, iron and manganese.)
Chrysoberyl (varieties: chyrsoberyl and Alexandrite) are: Be4Al2O4 -- chemically classed as beryllium aluminum oxides, and those atoms are put together according to the orthorhombic crystal system plan. They have a hardness of 8.5
These two mineral have many other physical, chemical and optical differences such as their birefringence, dispersion, luster, specific gravity, etc. Also they are found in different types of rock deposits in different parts of the world. Great question!! Thanks.
If I want to determine if a glassy mineral in my hands is a diamond, what simple test might help me?...Marie, USA.
From what you ask, I will assume that you have an uncut mineral specimen and not a faceted gemstone. I"ll take your question to be, then: Let's say we go out gem digging and find a "glassy" piece of material -- could it be a diamond? You don't say where this was found, so for the sake of simplicity we'll be in "diamond country". Actually, even without fancy equipment there are a few tests we could do that might help.
1) Natural diamond crystals can come in many shapes but some of those shapes are fairly common and recognizable, like cubes and octahedrons -- do a google image search on diamond crystals, and see if any of the shapes look like what you've got.
2) You can do a crude hardness test with a tempered steel file -- if the specimen cannot be scratched with it, then it is harder than 8 and could possibly be a diamond ( it could also be a white topaz or a white sapphire)
3. Diamonds are notoriously grease loving. Put a thin layer of petroleum jelly on a piece of cardboard and gently lay the specimen on it and turn it upside down. If the piece sticks pretty tight it could be diamond (size and weight of the piece may make this test unreliable), if it falls off quite easily then it is probably not a diamond.
4. If the piece has any shiny faces, look at the luster -- the luster of an unpolished diamond is quite distinctive -- sort of like a greasy/metallic shine, not at all like the glassy luster of quartzes, topaz and most other gems.
Beyond this you'd have to do specific gravity determinations or other tests that require gemological equipment.
What separates green grossular garnet from tsavorite garnet? In other words, what makes a green grossular tsavorite? And what makes other green grossulars not tsavorite?...Diane, California
Tsavorite is defined as green grossular garnet, colored by vanadium, and of medium to dark color. If the grossular garnet gets its green color from an element other than vanadium (very rare) or, as is more commonly the case, is lighter than medium green, it is just called green grossular. Sometimes "mint green" or "Merelani Mint" is used as a trade name for such stones.
It's kind of like the nebulous and movable dividing line between pink sapphire and ruby, and between green beryl and emerald -- it's primarily a color thing -- and there is no hard and fast definition. I've seen people sell "Tsavorite" that I would call green grossular, and "ruby" that I would call pink sapphire. I guess in this case we can modify the old joke about pink sapphire/ruby to: "Whether a stone is a Tsavorite or a green grossular, depends on whether you are the seller or the buyer".
I was at a jewelry store today and was looking at rubies. The ruby is my birthstone and I have 3 rings and a necklace that have pretty, red, eye-catching rubies in them. Most of the rubies at the store I was at were a dull, almost purplish color. When I said something about them looking plastic the girl said that that is what "real" rubies look like, and that synthetic rubies have the red, watery color. I've looked around online and everything I've found said that only a gemologist can tell the difference between real and synthetic, and that the redder a ruby the more prized it is. Could you please clarify? Can an ordinary person tell the difference?...Whitney, USA.
Rubies are the most valuable gemstone next to diamond. Their price is controlled by color (a medium dark red with a very slight purplish cast is ideal), their clarity, and their size. Rarity is directly related to price. Rubies of fine color that are completely transparent, and without visible flaws are very rare and therefore very expensive -- in sizes over a carat -- thousands of dollars per carat, and even larger ones, say 5 cts in size, are more expensive than comparable size/quality diamonds.
I tell you this so you will understand that the natural rubies you see in most jewelry stores that are being sold at anything like reasonable prices are what's known as "commercial quality", not "gem" quality. They are translucent rather than transparent (due to many microscopic inclusions), their color is inferior: usually brownish or too purple or too dark or too light, and they may have visible inclusions. Although it sounds to me like the clerk at the store was being a bit rude and somewhat condescending, what she said was basically true.
Synthetic rubies, of perfect color and clarity can be made in any quantity desired, so they lack the rarity, and therefore the value, of gem quality natural stones. They are rubies, though, and have all the chemical, optical and physical properties of natural ones.
If what you are looking for is a fantastic colored, clean, ruby at a minimal price, and the fact that it was made in a laboratory doesn't bother you, then enjoy the synthetics. If on the other hand you long for a natural stone and don't have unlimited funds, you may have to choose a jewelry piece with a cluster of good but tiny natural rubies, or if you want bigger size, settle for stones which have less transparency or less than ideal color.
Yes, It is generally true that it takes gemological knowledge and equipment to absolutely discriminate a synthetic from a natural stone. A reputable firm will always tell you the truth in their advertising and store labeling, and when you ask, if a gem is natural or synthetic in origin and whether it has been treated or enhanced in any way.
PS. Ruby is my birthstone too!
If you'd like to know more about our birthstone, you might enjoy viewing this pictorial essay on ruby:
I am a recent fan of your website. It is very refreshing to get clear, honest, information from a qualified gemologist who is willing to share with amateur collectors such as myself. I have collected several types of quartz, and am particularly fascinated by rutilated quartz. I understand that quartz with the golden rutile needles is called rutilated quartz, and that quartz with black or dark needles is called tourmalinated quartz. My question is, how do these needles form inside the quartz crystals? I am going to do a presentation to a school science class on quartz, and would like to be able to explain the phenomenon of the needles.... Joelle, USA
Thanks for visiting my site and for the kind words. Quartz is a gem which forms by precipitation from a liquid solution, in the case of rutile which has similar formation, the scenario goes like this: In an underground cavity a water solution which contains the ingredients for both quartz (silicon and oxygen) and rutile (titanium and oxygen) begins to cool. Rutile crystallizes first as needle-like crystals, and then as the temperature of the solution continues to lower, quartz crystallizes around it encasing the already formed rutile. With tourmaline, which generally forms from cooling magma, we can, instead, picture a cavity containing pre-formed tourmaline crystals which is later invaded by a solution, which then forms the quartz around the tourmaline needles. Tourmalinated quartz is much less common than rutilated.
I've purchased some inexpensive black onyx jewelry created in Thailand but sold by a vendor in the U.S. to sell on my website, and I've also purchased a bracelet at a jewelry show in Las Vegas and I'm wondering how you can tell fake black onyx from the real thing? I'm concerned that it might be easy to fake, and that what I have could be epoxy or some other substance. Some of the jewelry is flush with the setting and looks too perfect....Sandy, USA.
You are correct to assume that black onyx can be, and has been, simulated by many materials. Although the real deal is pretty inexpensive as gems go, glass and plastic are cheaper -- so there is money to be made in deception.
My first question might be: is the jewelry set in sterling or karat gold? if so, the gems are more likely to be genuine. Plastic will feel noticeably warmer to the touch than either black onyx or glass imitations. If you can sacrifice a piece, you might whack it with a hammer it until it breaks, then examine the broken surfaces. Both real black onyx and glass will break with a shell-like fracture pattern that has a shiny surface-- plastic will have a dull granular looking fracture that is irregular. On the thin edges of the broken pieces use a strong light and a magnifier, and see if you can see either some bubbles or translucence, in which case, it is probably glass -- true black onyx would never have bubbles, and should be opaque even in thin areas.
Years ago I found a pearl in an oyster my mother had made for our supper. A jeweler told me that the pearl no longer had any value once it had been heated. I just would like to confirm or deny this information. Could you help?...Faye, USA.
Your jeweler was partially right, but he didn't go quite far enough. There are many different species of mollusks that are loosely called "oysters" and all of them are capable of making solid objects in response to an irritant that enters their bodies. Not all of these solids are classed as pearls. That term is limited to those which are made of nacre (the "pearl-like" surface on gem pearls). Other types without nacre are called "calcareous concretions" and most are not beautiful or valuable in any way (although the queen conch snail, giant baler snail, and the scallop all produce concretions of beauty and value). The species of oysters that are harvested for food do not make "gem" pearls, nor are their concretions valuable -- so whether the piece had been cooked or not the "pearl" from one of those would have been a chalky dull thing. Natural and cultured gem (nacreous) pearls from inedible "pearl oysters" are formed from combinations of a mineral (aragonite and/or calcite) and mollusk protein (chonchiolin). Protein is easily damaged by heat and so, if by chance, a gem pearl were boiled in soup or fried in oil--> (perhaps your pearl earring fell into the stew pot) it would surely be ruined.
I am planning on buying a graduation gift for my 15 year old granddaughter, and was looking into a strand of 16 inch cultured pearls for her. I have been to a large dep't store who had a big sale (50% off) as well as several jewelers. Prices have varied from $1000 to $150 for cultured which leaves me scratching my head as to the large difference. The "jewelers" also mentioned the sizes govern the price. Is there a way for the average consumer to identify the "real Mccoy"? or am I at the mercy of the seller?...Bob, Florida.
I don't want to inundate you with so much information that you're swamped, so I'll try to be as brief as possible -- but buying pearls wisely is not a simple matter.
In today's world of department store and shopping mall jewelry stores "50% off" is the norm. Their profit margins are the same as they ever were. Pay no attention to that: once you've determined the size, type and quality of pearls you want, then you can do some price-comparison shopping.
You say that you want to make sure you are getting the "real McCoy", not plastic, shell or glass imitations, and that part is easy. Any reputable vendor (store, established internet site, etc) has to abide by the Federal Trade Commission rulings on advertising, and must therefore use words like "imitation" "simulated" or "faux" in their descriptions of simulants. (Look for a label, a printed sign or advertisement, don't just take a salesperson's word for it). The term to require is "cultured" if you want a "real" pearl. Items sold at swamp meets or through individuals advertising in newspapers are MUCH more likely to be misadvertised, either intentionally or not, so make sure you are doing business with someone who is going to be around in the next several years, and who offers a guarantee of satisfaction.
As far as the range of prices you quote, this is to be expected, as the value of pearls varies due to a number of factors. In a nutshell: cultured pearls of the type you are thinking of getting for your granddaughter come in two major types: freshwater, and saltwater (often called Akoyas). Quality/price factors are determined primarily by the amount of time spent in culturing the pearl, the longer it stays in the mollusk the thicker the "nacre" (pearly luster) and the higher quality the pearl-- so the more it will cost. The size is controlled by the species of mollusk and size of the bead (in saltwater types) that is used. The larger the starting bead the bigger the pearl and again, the more expensive. Beware: you can find 8 mm rounds that have poor quality nacre because they were not cultured very long, and 6 mm ones of superb quality because more time was taken in growing them. My advice would be to go for first for higher quality, and make size a secondary consideration. Thick nacre layers increase both beauty and durability, which can be an important factor when buying for a young person.
A freshwater pearl is created by simply putting a piece of the tissue from one mollusk into the mantle of another. They grow quickly and many can be harvested from one animal. They come from various areas, but primarily from China. Naturally, they range in color from white to cream to tan, pinkish and silver but they can be dyed just about any color. If you want natural color pearls be sure to indicate that to the seller and have them state "natural color" on the receipt. Freshwater pearls are not yet produced in the perfect roundness of saltwater types, but they are very close and usually have wonderful luster -- best of all they are inexpensive. $100 - $150 should buy you a 16" strand of good quality 6 - 7 mm freshwater cultured pearls. Saltwater pearls, (those which start out with a bead) grow slowly and usually only one pearl is harvested per animal, so they are more costly than freshwater -- the most admired, painstakingly cared for, (and expensive) of these is the Mikimoto brand, and a 16" strand of 6 -7 mm rounds could cost you $1000. Other companies sell saltwater pearls produced to less demanding standards, so you might find $200 - $500 strands of Akoyas. with other brand names.
One other type I didn't mention is the tropical, Tahitian or South Seas pearl, these large exotically colored (black, gold, silver) are very expensive and probably not the best choice for a young girl.
Pearls are delicate and require gentle wear and periodic re-stringing, so with a recepient of age 15, my personal recommendation would be to go with freshwater pearls which look wonderful, but require relatively low investment. If she follows in the footsteps of most women, as she matures, she'll acquire a wardrobe of different types of pearls, but she'll always treasure that first classic strand.
Two good books on the subject are: Renee Newman's Pearl Buyer's Guide, 4th Ed. and The Pearl Book: The Definitive Buying Guide, 3rd Ed. by Antoinette Matlins (both are available through amazon.com and other internet vendors)
My 5 year old daughter loves rocks, loves collecting them. She likes to sneak them to bed or in her backpack to preschool. She found this big hand-sized rock in the water at the beach, I let her take it home, and it's still one of her favorite rocks. She was fascinated by a show, I think on Discovery Channel recently, that talked about Jade, fixing it up and such. I would love to see how far her interest goes with this. Do you have a recommendation/starting point for children interested in geology?...Andrea, USA.
You are to be commended for wanting to encourage your daughter's interest. Most of the great artists, scientists, and athletes in the world had parents who did the same.
A great point to start is to get a book. Even though much of the content will be over her head for a while yet, The Smithsonian Handbook of Gemstones and another from the same source on Rocks and Minerals are picture-filled books that she can grow with. Search Amazon.com or one of the other internet booksellers under their juvenile category for kids' books on rocks and geology, too.
If you live in, or near, a good sized city you probably have a Natural History Museum, which will let her see rocks, minerals, fossils, and objects made from them at first hand.
The International Gem Society www.gemsociety.org has a section called " Gemology for Kids" and the magazine "Rock and Gem" available at larger newsstands, has a page in each month's issue devoted to young readers.
The simplest activities involving rocks are collecting and tumbling. At her age she could arrange her collection by color, size, place collected or whatever she wants -- later as her interest matures she could get into the scientific part of it. Try the internet auctions and search for ready made "rock collections". A small beginner collection might thrill her, and she could add to it, rather than start from scratch.
Tumbling rocks is time consuming (takes several weeks) and somewhat noisy and messy, but kids love it, and the smooth, shiny products can be used to decorate flower pots or aquaria, or glued into bellcap settings for keychains or pendants. Again, the internet auctions and bookstores are good sources for "rock tumblers" and books on the subject, respectively.
Hello, I received a beautiful ring with a big blue zircon stone in it. The stone sustained some slight damage on the side...I must have hit something and the stone chipped at the edge taking along with it a chunk of stone from beneath the edge. Can this be repaired or smoothed?...Frances, USA
Blue zircons although relatively hard as gemstones go (~ 7.5), are somewhat brittle due to the effects of repeated heat treating required to achieve the blue color. This leaves them prone to facet edge abrasion and even chipping.
Yes, the stone can be repaired. The question would be how much of the stone would have to be removed to accomplish it, and what would that do to the gem's overall size and shape. Depending on the size and location of the chip, it might be possible to simply place an extra facet or two to cover it, or it might be necessary to recut the entire crown and/or pavilion. Recutting, even when done skillfully usually reduces the diameter of the gem. It is possible that it would end up too small for that particular ring setting.
In general blue zircons in rings should have protective settings (bezel settings are preferable to prongs) and they should be worn occasionally, not 24/7. If you have the stone repaired and wish to wear it daily, you might consider having it reset into a pendant mount which would be safer for it.
What does it mean when they say a gemstone is "coated"? Saw a pink sapphire ring advertised as "coated" and price was too reasonable to be true??? Thanks...Lydia, USA
A coated gem has a layer of paint, lacquer, or more often these days, a thin layer of metal created by vapor deposition on its surface. I am not aware of any cases where the coating process in use on sapphires (but there's always a first time). At present quartz and topaz are the most commonly coated gems.
Coatings are the most fragile of all gem treatments as they are only a micro-layer and scratch or chip off easily. I can't really see the point of doing that to sapphire (the second hardest gem), as there are other enhancements that can change color without making the gem so much more fragile. Perhaps the term "coating" is actually meant to designate diffusion which is a heat treating method that can penetrate the surface of an otherwise poorly colored sapphire to give it a thin layer of rich color. Such stones are generally quite inexpensive compared to naturally colored ones.
You might also consider that the "sapphire" if that is what it is, could be synthetic sapphire. Huge quantities of synthetic sapphire in a variety of colors are made and sold at prices from dirt cheap to nearly that of natural origin, (depending on the seller, the synthesizing process, and the size and color.)
(Note: this is actually a discussion comment posted by one of the students in my on-line gemology course, that I wanted to share with you)
This website sells the "Diamond Hybrid" and it is clearly a synthetic gem, yet their use of "GIA Grading Reports" and "Gemex" make it seem as though this is really a diamond. It's a little deceptive and I can see where the average person, who has not taken a gemology class would be confused and perhaps think this is a naturally occurring diamond...Luis S., Las Vegas, NV
I've had occasion to interact with these folks previously, and although it does not say it anywhere on their website, a call to a technical person at their factory confirmed that the "core" is cubic zirconia. This jives with their promotion of the gem as "as hard as sapphire" and singly refractive. Diamond HybridTM is actually a type of diffused or coated stone that has a micro-thin layer of what's called "amorphous diamond" embedded in the surface. Similar technology is used to make diamond coated surgical instruments, and for other some high tech cutting tools.
You are correct in your recognition that the comments on the website are deceptive: GIA does not grade synthetic or simulant gems with their "Diamond Cut Grade/Report" -- nor do they issue a brilliance report on a cutting style (like the princess cut) -- just individual diamonds.
These "gems" are quite expensive compared to CZ and, to each his own, but I've seen one close up and cannot imagine why anyone would want to pay that much for a diamond simulant.
What is the safest way to remove pearls from a setting (post only setting), so they can be put on a new setting? I would like to place the pearls on a platinum post. My wife has some beautiful pearls that we purchased some time ago. When we purchased them, we asked the jeweler to use 18K gold posts because the 14K posts tend to bother her. When he put the posts on, it appears that he just clipped the old posts and soldered on 18K posts. The solder bothers her ears as much as the 14K gold...Mike, North Carolina.
I'm amazed that the jeweler was able to protect the pearls adequately from the heat of the soldering process! Generally, those posts are secured with an epoxy adhesive which can be removed by soaking in a non-acid (acetone based) solvent, then the entire back assembly would be replaced and re-epoxyed.
In the meantime, here's a simple "work around" for her metal allergy that should give her immediate relief: carefully paint the metal and solder on the back of the earring with several thin coats of clear nail polish. Once dry, this will form a protective, unobtrusive, and fairly long lasting barrier. The nail polish can be renewed periodically, if desired, and would be eventually be removed by the same solvent the jeweler uses to de-glue the post.
How worried must one REALLY be about thermal shock when wearing semi-precious stones such as topazes, quartzes or amethysts outdoors in cold weather? For example, if I wore bezel-set blue topaz stud earrings outside to run some errands and it's 28 degrees outside, could I crack them simply by walking into my heated apartment?...Brookes, USA.
Don't worry at all. Those gems have been through a lot worse in the natural environment when they were formed and mined, and later at the hands of the lapidary when they were cut and polished.
Thermal shock would be a factor with MUCH greater temperature changes than those. For example, if you heated the stones in an oven at 500 degrees and then threw them into ice water, there might be a problem, or if a jeweler used a torch to resize or repair the jewelry without using a protective gel on the stones.
By the way (no extra charge) :-) the term "semi-precious" is rarely used by gemologists these days. It is akin to "damning with faint praise", and not reflective of the true value picture in the marketplace. There are rare or high grade quartzes, amethysts, tourmalines, garnets, feldspars, and other " non-big four" gems that are much more valuable than medium to lower grade pieces of what used to be called the "precious gems" (diamond, ruby, sapphire, emerald). The preferred term now for all species from agate to zircon is just "gemstones".
I know that a well-cut stone should not display a window. I think I have read on your site that if you can read newsprint through a stone, it is windowed and thus not cut correctly. I'm wondering if it is considered windowing if the type is distorted. Is a stone considered windowed if you can see anything at all through it? What about the color of your finger through a light stone?
Also, I have a few topaz stones that I have bought that were called untreated blue. It's true they are light blue, but they were advertised as untreated. In reading your answers to other questions I noticed that you do not list blue as a natural color for topaz. Can it be natural, or have I been fooled?...Julie, USA.
Let me start with the color question: there are light blue topazes in Nature, but they are rather uncommon. It takes a specific combination and timing of heat and irradiation to make a topaz blue, and in the types of deposits where topaz is found those rarely occur. I cannot say for sure whether you were "taken" or not, and I know of no ordinary gemological test that will tell. Unless you obtained your specimens from a reputable dealer who specializes in rarities, and they gave you a written guarantee, I'd bet that the stones are enhanced. The dealer may not be the bad guy, though, as most are not trained in gemology, and they take the word of their trusted suppliers who take the word of their suppliers....etc, etc. The true provenance of many gems gets lost somewhere along the way.
In regards to windowing: A well cut stone should reflect so much light from its pavilion that nothing is seen behind it, neither distorted print, nor flesh color. This statement presumes however that you are looking through the stone with your eye directly above the table and it is not tilted at all. Tilting the stone even slightly will change the angles of light hitting the pavilion facets and it may window.
Each type of gem has its own range of "tilt" brilliance. The lower the refractive index the less tilting it takes to window the stone. Let's compare two stones: diamond with a very high RI, and quartz with a rather low one. If both are cut to perfection, you will be able to tilt the diamond quite a lot without windowing, but the quartz only a little. Topaz has a high RI (not as high as diamond, but up there) so a well cut stone should not window easily from tilting -- from your description it sounds like yours have been cut to sub-optimal angles, and therefore are either windowed face up, or with slight tilting.
(Another important factor is cleanliness -- a layer of skin oil, soap scum, or hand lotion on the surface of a gem can substantially lower its RI -- diamonds are notoriously grease loving and it takes frequent scrubbing to keep them clean!)
One more point: We say cut "properly "or "to perfection", but we should keep in mind that there can be other goals in cutting a stone besides brilliance. In some times and/or places, windowed stones have actually been preferred because they maximize the weight, and usually the face up size, of a piece.
You should take into consideration that if your windowed stones were recut, to "correct" angles for maximum brilliance, you could lose up to 40%, or even more, of the carat weight, depending on how badly windowed they are.
I've just had a ring valued, and was told it was an antique synthetic spinel diamond ring. What is meant by synthetic spinel?...Jo, ?
Around 1920 the natural gemstone, spinel, was first successfully synthesized in a colorless form (many colors of this gem occur in Nature, but white is not one of them). It was very shortly thereafter put to use as an inexpensive simulant for diamond. This is analogous to the way cubic zirconia (CZ) which wasn't invented until the 1970's is used today. White synthetic spinel is still manufactured, but as it has little dispersion (fire), it is not very convincing as a diamond simulant compared to CZ, and now the latest contender Moissanite, which have higher dispersion, so its use is minimal.
I think your appraiser is saying that the ring which is antique (or vintage, perhaps, would be more correct, as the term "antique jewelry" is usually reserved for pieces 100 years old or more) has synthetic spinels in it to simulate diamonds.
I have been looking at your website. Very nice. The editor of our rock club bulletin included it in the latest issue. I have a question for you. If I were to take a stone to a jeweler who says he is a gemologist, is it necessary for him or her to keep the stone overnight or a couple of days to determine what the stone is? I am especially concerned as the stone could possibly be fairly valuable. It is quite unusual in that it is marquis cut, however it is quite tall and has no faceted edges. It is red in color much like garnet and very clear. Thanks so much for your help in advance...DD, USA
Thanks for visiting my site and for your kind words.
I can't think of any common tests, off hand, that require an overnight time frame, but the combined time for a number of individual tests may add up to a couple of hours. If the jeweler has a diploma from GIA or other recognized school of gemology you might check to see it. Just saying you are a gemologist doesn't make you one.
Many jewelers and gemologists do what is called a "take-in" sheet with weights, measurements and an inclusion plot on it so that you can be assured that the stone you get back is the one you gave them, and the jeweler is also protected against false claims to the contrary.
It might be wise to have the jeweler "clear the schedule" so that he/she can do the tests without being constantly interrupted by other customers to minimize the time frame (but be aware that that might also increase the professional fee for the identification).
I have been seeing some stones set in jewelry labeled "green amethyst". They're in the Ross-Simons catalogue. You can see it online as well. What's your take on that?...Annie, Las Vegas, NV
There is no such thing as green amethyst gemologically. The definition of amethyst is in its purple color. Sellers sometimes take liberties with gemological naming conventions to "romance the stone": other similar examples include "white aqua" for Goshenite, and "red emerald" for red beryl. Prasiolite quartz is a green variety that occurs naturally but rarely. Some amethyst from a few mines in South America can, due to its unique chemistry, be heated to a green color and is sold as prasiolite (occasionally it is called "greened amethyst)". QVC sells the heated type and calls it prasiolite, but it sounds like this company is calling it green amethyst instead --> pure advertising blather!
I really like your site...here is my question: Is Peruvian Opal really an Opal or is it just some other stone that is called Opal (like "New Jade" is really Serpentine)?...Petra, Los Angeles, CA.
Yes, Peruvian opal is real opal. It is usually blue and may be opaque or translucent. Some pieces have dendrites of black manganese oxide in them. Less common, but also attractive, are the pale to medium pink opals from Peru. I recently ran across some extraordinary pieces that were a mint green in color.
The Peruvian material is what is referred to as "common opal" because it does not have color play like the "precious opal" that comes from Australia and other areas.
You are quite right to be on alert when you see an adjective in front of a gem species name, though, as a lot of them like your example "New Jade", "Swiss Lapis" (dyed howlite) and others are trade names or misnomers for simulants, rather than true variety names.
I have what was a beautiful amethyst, about 2.5 carat, emerald cut. It became cloudy all over, and no one has an answer. Given the hardness of 7, what could I have done to it? My husband plans to replace it, and I don't want to repeat my error. It is in a platinum and diamond setting. Thanks for your help....Ann, USA
Although it is hard to make a judgment without seeing the piece, there are two main possibilities that come to mind, based on different scenarios.
1) If, by cloudy, you mean the stone went from transparent to translucent -- then the only thing I can think of is "crazing". When a gem is heated and cooled rapidly the thermal expansion and contraction (especially if there are inclusions) can create a network of stress fractures that give the stone a cloudy look. Did you take the piece to the jeweler for repair recently? Diamonds and platinum are practically heatproof, but amethyst is not. A jeweler's torch could supply enough heat for crazing if the stone were not properly shielded.
2) The other alternative would be that the cloudy appearance is confined to the surface, and just represents accumulated wear and tear which caused the amethyst to lose its polish and become dull and "frosted" looking. There is no commonly used cleaning solution that would "etch" the surface, although Lava soap, Comet cleanser and some other household products that contain abrasive particles could do damage over time. Amethyst, at hardness 7, cannot be worn daily in a ring or bracelet setting without, over time, getting dull and scratched.
When you replace the stone take care, if it is in a ring or bracelet, to wear it just occasionally and advise any jeweler working on it to remove the stone during the torch work and reset it afterward. For 24/7 wear, especially in a ring or bracelet, it is best to stick with gems that are either exceptionally tough like jade, or have hardness 8 or above like chrysoberyl, corundum and diamond.
I have heard from numerous people that blue green obsidian is real & then on the other hand it is fake (man-made glass). Have you heard of this ? Is it REAL OR FAKE? MAHALO NUI LOA, ...LINDA,HAWAII
As far as I know there is no natural transparent blue-green obsidian, although a lot of "volcanic glass" of that color is sold, in the form of carvings, in rock shops. This is, as you say, just plain old man-made glass. There is however, some opaque obsidian from the American southwest and Mexico that has a blue green iridescence, called rainbow obsidian or velvet obsidian, as seen in the attached photo, and it is a natural stone.
Can you tell me what a ring is made of. It's stamped 14K Pat-P. Thanks...Pam, US
It means that the piece is 14/24ths gold. Another way to think of it is 57.5% gold. The rest can be silver, copper, nickel or other metals depending on the color and characteristics of the alloy. Except for the US, most of the rest of the world uses parts per thousand as the quality mark for gold, in this case that would be 575. The Patent Pending mark, might be for the design of the ring, or possibly for the special nature of the gold alloy.
Hello, Great site! Just wondering if you can tell me what some markings mean on a pearl necklace I picked up at a garage sale. An elderly lady had died and the family just wanted to get rid of everything in the garage sale. The pearl necklace has 105 pearls about pea size, with a gold slide-lock clasp that is in the shape of a football, on the side of the clasp the numbers 14/20 and then a design "similar" to a Y or fancy T shape. Could you tell me what those markings mean? ...Cindy, US
The marking is to indicate that the material is what is called either "rolled gold" or "gold filled". 14 refers to 14k gold, and 20 means that 1/20th (5%) of the wire or sheet it was made from, consisted of 14k, either roll-bonded on in a layer, or in some cases electroplated, the rest is base metal (usually brass). The fancy Y (has what looks like an = sign through the top, and is part of the mark. Although it is possible the pearls are cultured, they are probably imitations, as cultured pearls are usually set with 14k or better -- especially the older ones.
You can do a quick tooth test on the pearls: Run a pearl over the edges of your bottom teeth -- if it feels slightly gritty = cultured pearl, if smooth = imitation.
I WAS RESEARCHING A COUPLE PIECES OF JEWELRY THAT I INHERITED. I HAVE TWO PIECES OF JEWELRY THAT WERE ORIGINALLY FROM HELZBERG, THE PAPERWORK IS WITH THEM. IT SAYS THEY ARE "ROYAL AZEL". THE PRICE ON THE PAPER WORK IS PRETTY HIGH SO I WAS ASSUMING THEY WERE A RARE GEM. CAN YOU TELL ME IF YOU KNOW ANYTHING ABOUT THE ROYAL AZEL AND WHAT THESE PIECES MIGHT BE WORTH? I HAVE A NECKLACE THAT IS ABOUT 1 1/2 INCHES TRIANGLE SET IN 14K GOLD WITH ONE DIAMOND AND A RING THAT IS A ROUND STONE WITH THREE DIAMONDS. THANK YOU FOR ANY HELP YOU COULD GIVE ME....??, Denver
"Royal Azel" was a trade name for high quality sugilite circa 1990s, that has since fallen out of fashion. The material is now generally just called gel sugilite or gem sugilite. Sugilite is not an extremely rare gem, but it is, in its highest grades, quite expensive for a non-transparent material. (Ballpark on retail @ $15-50/ct.)
Since the value of jewelry is determined by a number of interacting factors: age, metal content, workmanship, stone quality, etc. I cannot tell you what these worth -- if you think the value is considerable I'd suggest you go to a certified gemologist/appraiser and get a value. (The pieces cannot be very old, though, as sugilite wasn't a factor in the gem market until about 20 - 25 years ago.)
Here's a link to an essay I wrote on sugilite that might interest you.
What type of mounting would I need for an antique cut stone...mine cut or cushion cut looking...Alice, US
In general a rectangular or emerald cut prong type mounting can be used (in some cases an oval will work) -- but any of these would have to be adjusted by a jeweler or metalsmith to fit properly. In the case of a very short antique cut (almost square) a square or even a round prong setting could be adjusted. If you want a bezel setting though, you'd need to get one custom made for the stone.
Thanks for the wonderful answers to gem questions. I saw your many answers about cut stones, and they give some clues, but I wonder about my collection of star sapphires, which I bought in Chanthaburi, Thailand. One lot which I bought is navy with a star that is so brilliant it can even be seen under fluorescent light. There is no star present when I put the stone in a darkened place, so I am sure this is a refractive star. But I have been told a brilliant star may be the sign of a synthetic stone. I have photos of them online at http://howeird.com/gallery/Sapphires/index_3.html ...Howard, California.
Thanks for the kind compliments and for sending the link to the photos. I must include my usual disclaimer that without physically testing a gem I cannot make an identification, but the photos you sent are pretty informative.
Background: Star sapphires come in four degrees of "alteration".
1) Natural origin, unenhanced: these are untreated in any way, and except for cutting into cabochons, just as Nature made them.
2) Natural origin, enhanced with heat: the rutile that makes the star by reflection (not refraction, BTW) is a separate mineral which can exist in sapphire in a dissolved state or precipitated as needle-like crystals. Some pieces which contain rutile have it in both forms. Treating such stones with a very specific heating/cooling regimen causes some of the dissolved rutile to form crystals (by a process known as exsolution). This enhances the star.
3) Natural origin, enhanced by diffusion: some stones have too little rutile to form a strong star. These can be made into star stones by super high temperature heating in the presence of powdered rutile (titanium oxide). At close to the melting point of the sapphire, some of the rutile migrates into the surface layers and precipitates upon cooling. Such a piece can be cut into a star stone.
4) Synthetic origin: these are man-made "from scratch". Powdered aluminum oxide and rutile are melted and cool into sapphire crystals containing enough rutile to form a strong star.
In terms of value, 1 and 2 are relatively close in cost (lab certified natural, unenhanced stones go for about a 20% premium) -- but because over 90% of sapphires and rubies found in the marketplace are heated, it's actually prudent to assume that all corundum gems have been heated in some way. 3 and 4 are also close in value and at least one or two orders of magnitude less valuable than 1 or 2.
Now, as far as telling them apart. In your photos, the brown and gold and light grey blue pieces look obviously natural -- the bright blues most likely are not. Some of the signs of group 3 and 4 are legs which are very straight and evenly bright. Another is that the star shows up strongly in less than ideal lighting conditions. Diffused pieces, especially, (which I cannot tell from the photo, but which you should be able to see in person) give the appearance of the star being "on the surface" rather than coming from inside the gem. In general, I get suspicious when I see any group of "natural" stones that are so uniform in color and optical phenomena as yours. The vast majority of natural blue sapphires are more of a blue grey color, and lighter than yours. Also the intensity of the star tends to vary from stone to stone in any group.
If you got those stones in the 70's it's a little early for them to have been diffused, but I don't rule it out. It is not too early for them to be synthetic, though. (The Russians are supreme in the production of the synthetic gems, but the Thai's have long been #1 in enhancement -- using new treatments often not "discovered" by the rest of the market until long after they were invented).
To sum up, I'd say that on the basis of the photos, it is likely that your navy blue stones are either synthetic or diffusion enhanced, but the others appear to be natural and unenhanced.
I have several small clear quartz crystal clusters that are delicate and I would like to seal them. Do you know of any products that I could use to coat and bond the crystals without a cloudy finish....MJ, USA
If any pieces are loose or detached a tiny drop of superglue will secure them. For an overall sealant, try gloss or semi-gloss polyurethane spray varnish. As with any such project, try it on a piece you aren't crazy about first and do several very thin coats rather than a single heavy one.
I am trying to make some jewelry and I want to use some pieces of black coral, but I would like to know which would be the easiest way to cut and polish this coral in cabochons. I am new in this and I don't know if Ishould buy a machine to do this; I just want to keep it simple....Victoria, USA.
Black coral is made of a hair-like protein material, and is sensitive to heat, but it polishes to a gorgeous shiny black with minimal effort.
Use a small jewelry saw to gently cut the pieces into the size and shape you want. Begin to work them (dry) with 600 grit sandpaper (by hand is fine). Be sure to wear a dust mask and take it slowly, so that heat doesn't build up. Once the pieces are smooth, use 1200 grit sandpaper to make them even smoother. Do not use water as this causes the material to swell and it may crack.
The last stage is to polish them with "Zam" which is a metal polish that jewelers use (it is green and comes in a stick). You might be able to do this by hand with a soft cloth, but the polish will be much easier to get with a "buff" on some type of rotary tool. I would recommend a "Dremel" type which you can get inexpensively and which has a lot of other uses. Remember to go slow, and not let heat build up, and wear your dust mask, and keep the coral dry, and you soon should have "patent leather" shiny black pieces.
In the fall you posted information on an internet gemology course that you were teaching, and I lost the web address. Could you give it to me again? Thank you...Jeff, Florida.
This page will take you to a no charge, not-for-credit version, but if you want to register for credit, there is also a link to the college website for that. Registration is going on now, and the course starts Janurary 23rd for Spring, 2006.
I have collected several 'coral' pieces, mostly antique items. I have tried to do the test with the lemon juice but it wasn't always conclusive. I have now a bead necklace which is individually knotted with a 14 kt gold clasp and the beads are an off white, some have pink swirls through them and I am wondering if it's glass or coral (I bought them as glass because the lady thought they are too heavy for coral). Which one is heavier, cooler etc. Coral or glass? Thanks for your help....Ines, Australia
Without seeing the pieces I can only give generalities. Calcareous corals have a glassy luster on the surface if they are polished properly, so the polish luster is not a way to separate them from glass. Generally glass is heavier than coral, and coral is somewhat cooler to the touch, but neither difference is so extreme as to be obvious, especially if you are not intimately familiar with both in bead form.
I would expect lemon juice to be inconclusive as it is not really a strong enough acid to give a noticeable reaction. Dilute hydrochloric is what gemologists use, and since it will dissolve the coral (with bubbling) leaving a mark, you must use just a tiny drop in an inconspicuous spot and observe the reaction with a loupe.
I'd say the most helpful and least destructive test is to use a 10x loupe and good strong light. Glass at the edges of the bead holes, where the knots are, may show tiny conchoidal (shell like) fractures that have a glassy luster, or at the thin edges you may be able to see bubbles and or swirls. If the beads are coral any fractures will not be conchoidal and will have a dull luster. You might also be able to see pores, striations or other evidence that this is an organic material with a complex inner anatomy. I'd be interested to know what you find out.
Is it true the new birthstone for June besides Pearl is also Tanzanite. I keep getting conflicting reports. Thank you in advance for your reply...Sabina, from ?
I don't mean to sound flippant, but quite honestly the whole birthstone thing is totally made up anyway, so any group that wants to do so, can develop their own list. There is a duly elected group from the jewelry industry who is in charge of the "official" list used in the US and Europe. This group has recently added Tanzanite as an alternate December birthstone, along with the traditional turquoise, blue zircon and the relatively new alternate, blue topaz. This makes December the month with the widest variety of birthstone choices. To my knowledge there is no well known system in the US and/or Europe that uses Tanzanite for any other month. The traditional alternates for June (other than pearl) are moonstone and Alexandrite.
There are however other equally worthy systems, based on day of the week, hour of day, non-Western astrological & mythic traditions, etc. etc. My feeling is, if you like a stone, and want a special connection with it, if you search diligently, you find some system that will call it "yours".
If you haven't visited my Birthstone page, here's a link:
There are a number of jewellery chains in Australia that sell "Created" Mystic Topaz jewellery. Is this different from the Mystic Topaz you described in one of yor earlier responses? In other words is Mystic Topaz a "natural" stone that has been given a special coating? Or is the entire stone synthetic?...Linda, Melbourne Australia
Synthetic topaz has been manufactured for research and industrial purposes, but I know of none in the gem marketplace. The reason is that the colorless natural material is still much, much, less expensive.
What your chain stores are undoubtedly doing is misusing the word "synthetic". A synthetic gem has the same chemical and crystal structure as the natural counterpart. The term they should be using is "enhanced".
Enhanced gems are natural or synthetic gems which have had additional treatments that change their appearance or durability. Most likely these retailers are selling natural origin colorless topaz which has been enhanced by coating it with a thin metallic layer. This layer creates the iridescent effect on the gems given various trade names, most commonly Mystic Topaz.
Retailers often also misuse the term synthetic, when they should say "simulant". A simulant gem, is one that looks like another, and is used in its place, but is not the same material, for example yellow cubic zirconia is sometimes sold as a simulant for scarce and expensive natural yellow topaz (the official November birthstone). I've seen several cases where these stones have been called "synthetic topaz" which they are not.
Can you help me? I work in a store where we just got some sterling silver designer jewelry in that has some set stones which they called caramel cats eye. The buyer said it is a very rare stone...but I always understood cats eye to be a very cheap manmade stone. They even feel very light weight and look cheap. What exactly is cat's eye?...Lisa, USA
Long before humans began making synthetic and simulated cat'seye stones, Mother Nature has been making real ones. There are many different species of gems which come in cat'seye varieties but all of them are relatively rare. A cat'seye is simply a stone that has bundles of parallel reflective inclusions inside such that when the stone is cut in a domed cabochon, the reflected light is concentrated as a line on the surface.
I'm including a link to my essay on Cat'seye stones so you can see some pictures of the "real thing". Although some species are fairly light in weight (for example cat'seye opal), none are really cheap, and you rarely see a natural cat'seye stone set in silver.
On the other hand man-made cat'seyes are very common and very inexpensive in the marketplace. They can be made of glass or plastic or even a type of ceramic material. One good way to spot them is that the "eye" is extremely bold, and often the colors are flashy or even gaudy in comparison to natural stones.
When I was in a gem shop in Hatton Garden this summer the sales guy noticed the turquoise enhancer I bought from you last year - he was very complimentary, BTW - and tried to interest me in an expensive string of turquoise beads to hang it from. I said I couldn't buy one because having a tendency to eczema I had to wear greasy skin creams. He agreed, but then also said that because of this I couldn't wear pearls, coral, or any other organic material. This seems a bit harsh! Also, I have had a couple of FW pearl necklaces for several years that look fine to me. I always wipe them down after taking them off, but this is all I can do as I do need to wear the moisturisers, especially in the winter. What do you think? Are pearls really that sensitive? And coral?? Some potential purchases could be very expensive, so I'd like to clear this one up, and make sure I do understand the limitations on these gems....Denise, London, England
I do think your jeweler was a bit too harsh in his assessment of the damage to be done to pearls by your skin creams. After all, skin itself has oils --- and this is not to mention the oily makeup bases that are often worn. Your precautions of wiping the strands down with a damp cloth should be quite sufficient to ensure a long life for your pearls.
Hard corals (the calcium carbonate types) which take a good polish, should react the same as pearls, but I would imagine the proteinoid types like black and gold to be more absorptive and therefore more sensitive. I expect he overstated the case with turquoise as well -- especially if it has a protective paraffin wax coat. (You can apply this yourself by simply melting some colorless paraffin and brushing a very thin layer on the turquoise piece then polishing all of it off again after it solidifies. The micro layer that remains will seal the small pores that can pick up stains. (Safety demands that paraffin be melted slowly in a double boiler type set-up, as it is quite flammable).
I it would probably be a good idea, in general, to make sure that your skin creams are well rubbed in, and if you feel a greasy residue, perhaps blotted. Other than that, feel free to enjoy the organic gems.
I have a ring that I take in every 6 months to have it checked and every time it looks so much cleaner in the jewelry store than it does anywhere else. I only wear one other piece of jewelry, which is my grandmother's wedding ring. It is very small and has tiny chips of diamonds in it. It looks so good in those lights too. Is this an optical phenomenon? ...Pam, Las Vegas
I think we can all relate to this, but it isn't an optical phenomenon (like a cat'seye or shiller), its just optimal lighting, and nice clean gems and jewelry.
Lighting a jewelry store is a very serious and highly engineered aspect of the business. Different sorts of lights are used in different areas of the shop to show each display to it's best advantage.
Even a bigger part of it, especially with diamond jewelry is that the jewelry that is returned to you has just been freshly cleaned and the settings lightly repolished.
As we wear them all gems quickly acquire a layer of crud (technical term) :-) like dead skin cells, sweat salts, skin oils, food residue, cosmetics, suspended particulates from the air, etc. All precious metals are relatively soft and develop a fine surface network of scratches from contact with other surfaces. Both these things lead to a dull looking piece of jewelry.
Diamonds in particular are "lipophilic" which means that grease sticks to them very tenaciously. Jewelers often use steam and or ultrasonics to blast off this greasy layer. (Careful jewelers would not clean colored stones this way).
For a few hours or days after visiting the jeweler our jewelry looks pristine, but then the grime and scratches start to build up again. :-(
I was in your Intro To Gemology class in the fall 2004 semester. I have a question for you. Moissanite is lab created, correct? Is it DR and diamond is SR? I am asking because the company I am working for has a couple of sales people that are selling Moissanite as J color IF clarity lab grown diamonds. This is not legal is it? Any answers you can give me, I would appreciate. Thank you in advance, (Name withheld)...USA
What they are doing is absolutely illegal! Moissanite is a newly introduced diamond simulant made of silicon carbide. It is NOT a synthetic diamond and no reputable firm would sell it as one. AGTA and GIA won't grade synthetic diamonds for clarity or color, but EGL does. Even EGL doesn't grade Moissanite! Although it would be acceptable to say something like "if this were a diamond, the color would be J and the clarity would be IF" --the way the staff is doing it now is fraud.
Yes, it is DR (doubly refractive) with high birefringence and must be cut carefully on an optic axis so that the doubled facets don't show through the table. Diamonds are SR (singly refractive). A polariscope would give a typical DR reaction. You can use your loupe to verify the DR status of Moissanite. Turn the gem at a 45 degree angle and few the back facets through the side, you'll see doubling. It may be subtle in tiny gems but with .5 ct or more you should see it easily. Diamonds never show doubled facets no matter which way you turn them.
Diamonds do not conduct electricity (except for natural and synthetic blue ones) and Moissanite does --> so the use of a "new generation" diamond tester will easily separate Moissanite from CZ and other simulants. (The older types use thermal properties which will not discriminate this newest mimic). Your store may already have one of these, but if not, it would be a good investment as a salesperson doesn't have to know any gemology in order to use one.
By the way, I think Charles and Colvard company who are the sole manufacturers would be upset to hear of someone misrepresenting their perfectly legitimate product in this way.
What is your opinion of Moissanite and white sapphire as diamond simulants?...Gracce, The Netherlands
Moissanite is a much advertised, recently introduced, synthetic material. It is harder than any of the other diamond simulants and rather expensive. It usually also has a slightly yellowish color. I have nothing against it, as long as it is advertised and sold as a simulant, and not as synthetic diamond or natural diamond. They can be quite pretty. In my book, however, CZ (cubic zirconia) is just as pretty at about 5-10% of the price.
White or colorless sapphire is also a hard gem, and it can be natural or synthetic. It is nicely brilliant but lacks the dispersion (tiny specks of color) seen in diamond, CZ, or Moissanite. Again, as long as it is advertised correctly I'm all for it. Synthetic white sapphire stones should be very cheap, natural stones, especially larger ones are rather pricey.
Since you asked my opinion, I'll volunteer that my own personal favorite diamond simulant is white zircon, which, although softer than sapphire, is also a natural gem (heat treated), has a near diamond-like luster, and has very close to as much dispersion and brilliance as a diamond.
I have tried to read everything possible to distinguish the difference between Tanzanite and iolite, and the information in most of the gem books, doesn't really give you an answer. I know that I have some Tanzanite and iolite gemstones, but I would like to be sure that the stones that I think are Tanzanites, truly are Tanzanites and not iolites. Do you have a way of telling the difference? Thank you very much for your time...Clare, USA
There are gemological tests like refractive index and specific gravity which can give you a definite answer, but it should be pretty easy for you to tell the difference if you pay careful attention to the colors you see. If they are unmounted stones, turn them upside down (so as to minimize reflections) and in good light, slowly turn them 45 degrees at a time. Note the color at each turn. With Tanzanite you should see only shades of blue and violet, with iolite the changes should be more dramatic as you will see blue-violet, a greyish color and at some point the colors should fade to a noticeably lighter shade. In the face up view, no matter how you turn the Tanzanite you should not see any significant greyness, but with the iolite it should be there at some angles. You can do the same kind of test with mounted stones, but it's a little harder to see the differences, just turn the ring or pendant bottom up and go through the same series of observations.
I've heard some dealers and home shopping hosts promoting iolite as virtually indistinguisible from Tanzanite, but I do not agree, I always see some grey, even in the best iolites and I find iolite's color to vary more dramatically with direction than Tanzanite. Each has its virtues: Iolite is a tougher, harder and less expensive stone -- Tanzanite is softer, and more fragile (should never be used in rings!) but to my eye, at least in good quality, it is a more beautifully colored gem.
Here's are links to my essays on iolite and Tanzanite for further information:
Recently I came across a medium orangy red stone, presumably Mexcian opal that was domed on top and faceted under.
Its properties were: R.I. spot reading 1.46, Flourescence: Inert. Under 60x magnification, small isolated gas bubbles and color zoning and also a small area of dye-like looking concentration can be seen. The girdle was smooth. My main concern was that under the polariscope, when I rotate the stone, it shows snake-like bands.
My question is, could this be natural or glass then? I hear only snake-like banding shows in plastic or glass. My instinct says its natural-- I am so confused with this stone...Rahlia, Hong Kong
The snaky bands you see are called "anomalous double refraction" and are typical of Mexican opal. The fact that it doesn't fluoresce is also consistent with Mexican opal, whereas many plastics would. The RI is a bit high, but as it is just a "spot reading" I wouldn't be too concerned, since such readings only give an RI range.
Color zoning, even that which might appear dye-like is not unusual in these sorts of opals. The only thing that gives me pause is the bubbles: There shouldn't be any! Check them under the microscope with a polarizing lens, if they are actually rounded small crystals rather than bubbles, they should flash, dark and light, as you turn the lens, bubbles wouldn't do that.
Synthetic fire opal, which is a possibility, has been produced by the Kyocera company, but to my knowledge, has not yet entered the market in any significant quantities.
I was fascinated to read the question and answer session here. It's not too often someone is as helpful or honest. Thank you. I am a novice, learning slowly; my passion is colored gem stones.
Recently, I purchased a Nambian demantoid garnet-- it is 90 points for $100. The color is gorgeous medium, the dispersion is magnificant in my opinion. Prior to this I purchased a 40 pointer for the same price. Can you tell me why there was such a difference in price? The quality appears the same and both are very clean. One more thing: Are they valuable? I am crazy for this stone and just had to possess one.
Russian demantoi is out of my reach and I've only seen it in the museum. Can these gems be an investment for my children? Will they appreciate over time? Thank you again for your time and your column....Patty, New York
It's nice to know that you enjoying reading my "column". :-)
Prices for the less common gem species are not standardized. Very small differences in clarity and color can affect price dramatically, as can fluctuations in supply. Also, just like you, the gem dealer you buy from has to pay different prices from his/her different sources, and so might not have consistent prices.
You are correct in noting that Russian origin gems, at least at present, are the epitome of value for this particular species. Small pieces with good color and nice horsetail inclusions, are available, though, at least from some dealers at less than "museum" prices.
I never recommend gems as an investment, as there are just too many uncontrolled factors influencing their value up and down: mine depletions, new discoveries, political issues disrupting or enabling supplies, changes in fashion, etc. I cannot tell you (or myself) whether most gems will appreciate with time, or the reverse.
In my opinion, we all should just buy the gems that we like, at prices we can afford to pay, and then simply enjoy them. A wonderful endorsement for the purchases you've made of these Namibian demantoids, is your comment that you are "crazy for them". If, on top of that, they should appreciate in value, that's just the icing on the cake.
I inherited an aquamarine ring from my mother-in-law that she had since the late 1930's. She bought it in Brazil. I had the ring appraised by a gemologist and he wasn't quite sure that it was an aquamarine stone until I mentioned how old it was. Do you think I should get another opinion? Thank you for your time...Gloria, USA
Thanks for visiting my site and for your interesting question. I am wondering why the gemologist was unsure the stone was an aqua. The standard physical & optical tests such as refractive index, microscopic examination, specific gravity, optic character, optic figure, etc., should have been quite enough to identify it. Some tests cannot be done on mounted stones, though, which may have restricted the amount of information available.
I've also pondered why the date was significant. Perhaps the gemologist DID identify the stone as aqua, but thought it might be synthetic. Since beryls had not yet been synthesized in the 30's that could have cinched it for him.
Before synthetic stones were available, imitations like foiled glass and certain doublets were used as aqua simulants. In my collection of antique jewelry I have a 1910 gentleman's stickpin with a center "aquamarine" stone that is actually a garnet and glass doublet. The bottom is light blue glass which provides the proper color and a very thin, glued-on, top is made from a slice of garnet which gives durability. As you can see, it looks very realistic at a casual glance, but testing and microscopic examination quickly reveals it for the clever imitation it is.
If the gemologist/appaiser has credentials from a recognized organization like GIA, they have probably done their job correctly, but if you want to double check the results, I'd suggest you have a good jeweler dismount the stone and have the gemologist (or another one if you don't have much confidence in this one) check it again.
What exactly is a Diamonique stone made out of? I can't seem to get an answer, especially from QVC. They keep talking about the rough but don't give any indication of what it is. Please help...Valerie, USA
"Diamonique" is a QVC trademarked brand name for the man-made material known as cubic zirconia. HSN sells it under the brand name "Absolute". There are several large factories which make it and the marketers can either call it cubic zirconia, or give it their own special trade name.
This sort of "branding" happens in the grocery business with say, mayonnaise or peanut butter: different brands, same basic stuff in the jar. If you're in the market for cubic zirconia, just as with mayo, the "generic" form is cheaper than those with special labels. As QVC and HSN advertise, they have their own internal quality control process over the generic rough they buy, only allowing those pieces that meet certain standards to be sold under their house brands.
CZ is a diamond simulant that has no counterpart in Nature, with a hardness of 8.5 and more dispersion than diamond, it is also significantly more dense than diamond (weighs more per unit). For this reason the shopping channels sell their CZ by diamond weight equivalent size: you order a "1 ct" CZ piece and actually get a 1.65 ct. stone which is the same size as a 1 ct diamond would be.
Ever since the process for making it was first perfected in the 1976, it has become the diamond simulant of choice, and millions if not billions of carats of it are produced yearly. Rough CZ is so inexpensive that virtually all the value of the jewelry item comes from the cutting of the stone and the setting in which it is placed -- the cz itself has no "intrinsic value".
We found some raw/rough gemstones and would like to know how we can polish them ourselves. Any great ideas? .....Connor, USA
The simplest way to go is to tumble them. You need equipment to do it and it takes several weeks, but it is relatively inexpensive, and requires no great lapidary skill. To make cabs or faceted stones requires expensive equipment and some training. Go online and search for " rock tumblers" and "books on tumbling rocks". There are several inexpensive machines and good instruction books available.
If tumbling whets your appetite for more serious lapidary pursuits, you might visit a local Rock and Gem club meeting. There, you can ask members whether they have a "shop" or classes (most do) where new members can be tutored by older ones in the arts of cabbing, jewelry making, beading, and faceting.
I was wondering what the difference is between an amethyst and a rose of france?I just purchased what is supposed to be a rose of france but it is dark purple like an amethyst. Thanks for your time....Kristina, USA.
Rose d' France is a trade name that was invented a few years ago as a marketing tool in order to sell very pale amethyst. This comes under the heading of "romancing the stone". Your seller made an error in calling dark purple quartz by that name. Usually Rose d' France is quite a bit less expensive than darker stones, so if you paid a low price you might have gotten a bargain (unless the stone is so dark as to look black and then it's not worth much at all).
I hope this isn't a dumb question, but it seems difficult to get a straight answer on a question I have regarding clear quartz. I found some excellent quality clear quartz and am curious if there is any kind of market for this stuff. It is completely clear...some of it is really beautiful, of course, also I have alot of it that is either small or heavily fractured, for which I know there is no market. But the good pieces seem like they would warrant some demand. Is it worth getting the good pieces cut and shaped? Or should I do as one jeweler siggested and just toss them in the garbage? Thank-You for your Time...Thomas, USA
I think your question is actually a very thoughtful and thought-provoking one. What is beautiful? What relationship does beauty have to value?
Think of flowers for a moment: a rare orchid and a daisy from a field, might have equal claims to beauty on purely aesthetic grounds, and in fact you might find some who preferred the lines and color of the daisy to the exotic shapes and markings of the orchid. But which can be sold for more money and why?
In the gem world, rarity is the prime value setter, and as lovely as clean rock crystal quartz may be, it is very common (as gems go). There is some value to it, but so low that a great many pieces would have to be sold to earn just a little money. This is where the jeweler is coming from -- to him, it's only worth throwing in the trash. If you like the appearance of the material, and are willing to pay to have one or more pieces made up into jewelry or for specimens, you should go for it, but in reality, there is but a tiny market for such products.
You might enjoy reading my essay on rock crystal quartz (colorless quartz):
http://www.acstones.com/gemofmonth/2004/gemofmonth11.04.html linked here.
I would like to receive your views on the legal and ethical aspects of colour enhancement of sapphire by radiation...Samantha, Africa.
Thanks for visiting my site and for your question. In my view the answer is VERY simple. There is nothing legally or ethically wrong with selling or producing any gem with any enhancement as long as full disclosure is made (especially in regards to stability of the treatment), and the customer is paying an appropriate price for the type of goods offered. For a while there were some irradiated yellow sapphires in the market which faded in heat or light, but it is rare to see these today.
In regards to irradiation, the only special consideration is that the treated gems be monitored for residual radiation, and if present, held for the appropriate "cooling off" period to reach safe levels before sale.
I am hoping you will have some answers. How does one tell the difference between a gemstone and mere glass, especially if the purported gemstone is green and brown in color? What are the tests that can be carried out to verify their authenticity. How much should about 500 grams green gemstone cost?...James, ???
It is pretty easy to discriminate glass from real gems -- what is not easy is to tell a natural gem from a synthetic of the same species. You could have real gems, synthetics or a simulant like glass.
There are two simple ways and one not-so-simple one to tell gems from glass: the first you can do with just a magnifier -- a loupe or microscope. Focus on the interior of the stones -- if they are glass they should have at least some bubbles (rounded or oblong inclusions that look hollow) or swirls. If they are a crystalline material like quartz, for example. they would have more angular solid looking inclusions such as tiny included crystals.
Based on its thermal inertia, glass doesn't feel doesn't feel as cool as most crystalline gems to the touch, although it is not noticeably warm to the touch like plastic. This property is easy to misread, depending on room temperture, the settings the gems are in, and your own level of experience in testing it.
If you scroll down through this "Ask Barbara" page and look for my answer to Carmen in November, I describe how to make a home made polariscope with which you can test your stones. If they stay dark under "crossed filters" as you turn them, they are glass, if they blink from dark to light they are crystalline and therefore not glass.
If they are crystalline, you then need to determine the species and whether they are natural or synthetic. Tests like specific gravity, refractive index, and reaction to ultraviolet light can be done to tell one species from another. Usually only high power microscopic examination can disclose a synthetic, and sometimes that is inconclusive and the item must be sent to a big laboratory for analysis with high tech equipment. Gem identification is not a game for sissies! ;-)
As far as value -- the answer could be from pennies to millions of dollars depending on what they are: green glass or finest emeralds, peridots, tourmalines, synthetics, etc. If they are natural stones, the value could vary by orders of magnitude depending on nuances of their color, clarity and size.
Your best bet is to take the stones to a gemologist or jeweler/appraiser in your area for tests -- it's the only way to understand what you have and what they might be worth.
I'm just a beginner in the gemstone realm and will probably sound really stupid with this question. You list the carat weight of the stones in your descriptions, but on some there is ~ before the number. Could you please help me out with the meaning of this?! Thanx...???, US
Thanks for your question, which is not a stupid one at all. In fact, it was stupid of me not to define a symbol used in my descriptions! My highly accurate carat scale only reads up to 50 ct, so when I have a larger piece I weigh it on a less sensitive scale that reads in grams, then I convert the grams to carats by multiplying by 5. Because this is only an estimate, I use the symbol ~ to mean "approximately". Sorry for the confusion. While I'm at it, I'll mention that ct. tw. seen on some pairs and lots and some jewelry containing multiple stones stands for "carat total weight" and refers to the weight of all the gems combined. Thanks for pointing out my omission. :-)
Thanks for this page. I am a Bangladeshi. I was born in 1979 on late November, on Friday, on day time from 11:00 to 14:00 pm. So my question is which stone is appropriate for me? What are my characteristics in astrology sign?...???
Well, according to the European "birthstone" system, yellow topaz would be your birthstone, as it is for all born at any time during the month of November. I believe, though, that there are several other non-European birthstone systems which might be more detailed, by year, and/or date within the month, or hour of the day, and therefore more appropriate for your needs. I'm sorry to say I'm not familiar with them in any detail.
Also, I have no expertise in astrology, but I'm sure a little internet time spent using some of the search engines with input phrases like "gemstones + astrology" or "birthstones + astrology" will bring you access to many folks who are well versed in that field.
Greetings, I have some odd questions and I'm hoping you could help me find some answers. I recently stumbled across your website as I have been researching the topic of obsidian glass. I am curious about obsidian glass, I know it is formed somehow out of the lava or ash from volcanos, and I remember seeing it as a little kid when my dad took me hiking.
You see, I'm interested in purchasing a fairly large order of obsidian glass, I remember the unique qualities that it has and how it changes from pitch black to almost a hazy translucent colour, and I hope to use this in my art. I want to own my own art gallery, and I have decided to make it very unique by making the entire front side of the building out of obsidian glass, now I'm curious if this is even possible? I've only seen obsidian in small fragments, but my question is, near a volcano (dormant or active) can obsidian be harvested in large pieces? For instance, 20ft x 10ft x 1ft deep pieces? or maybe larger, and then be milled down to smaller sizes? Or is it only in fragmented parts? I have never seen any so large but that is roughly what I would like to do, I would appreciate any input in this matter. thank you for your time, and I hope to hear back from you soon....Leif, USA.
Volcanic glass forms when the lava from an eruption cools so quickly that normal crystallization doesn't occur. When the lava cools more slowly rocks like basalt are formed instead. I've seen obsidian carvings about the size of dinner plates but not much larger. I do not know for sure whether there are huge pieces, but the requirements of formation (the quick cooling) logically argue against them. Perhaps you could use smaller pieces in a kind of mosaic pattern, like stained glass rather than huge sheets.
Try "Bob's Rock Shop" http://www.rockhounds.com for further information -- it is one of the premier "rockhound" sites on the net, just bursting with information on minerals, their properties, and places where they can be collected or purchased.
What makes a stone, such as Tanzanite, usually enhanced to give it the desired blue/violet color, so expensive? Is rarity the only reason? Or is there something in the grade of zoisite material that influences the final color of the treated stone which leads to the increased expense for darker color? What about Blue Topaz, also usually enhanced? Thank you....Rita, Chicago, IL.
You ask a very good question -- at first it does seem illogical that two blue, treated gems should vary so greatly in their price per carat. Before I get to your specific question, though, let me treat your more general one:
In the world of gems, rarity is always a factor in value but it is not the only factor. Some extremely rare gems are relatively inexpensive (ex. Clinohumite) while some relatively more abundant gems (like diamond) are quite expensive. Popularity is also an important factor. In some cases extreme rarity actually hurts the overall value of a gem species. In such cases they are virtually unknown outside a small group of collectors and do not benefit from the boost in value that aggressive marketing can create. A gem is likely to be quite valuable if it is both relatively rare and quite popular and/or well known -- examples would be fine ruby (the world's most expensive colored stone), Alexandrite, demantoid garnet and Paraiba tourmalines.
Within a species or variety, color is a major factor determining value. In general, color purity (saturation or freedom from modifying grey or brown hues) is the most important aspect of color value, although hue ( color band in the spectrum) and tone (depth of color) cannot be discounted. (Of the basic spectral hues yellow tends to be the bargain color -- at least in my experience, yellow gems are harder to sell and bring less per carat than comparably colored gems in the other hues of blue, red or green.)
Tanzanite nicely illustrates the case when "taste" or preference enters the value equation. Tanzanites range in hue from slightly bluish violet to slightly violetish blue. Given equal saturation and tone, the bluer the stone the higher the per carat price. This value scale is not arbitrary, but based on the collective experience of gem dealers and jewelers with the preferences of their customers. Similar considerations make slightly purplish red rubies more valuable than slightly orangey red ones, and slightly violetish blue sapphires more valuable than slightly greenish blue ones.
Now to get to your specific issue: Yes, Tanzanite is very rare (also very popular), but it is especially rare in the depth of the natural brownish color which will heat treat to the desired rich blue-violet shades. Blue topaz on the other hand starts out as abundant and low value white topaz -- the major part of the value of a blue topaz gem is actually added by the treatments, which are rather expensive.
Berrylium treatment of sapphires: I purchased a yellow sapphire from a dealer who said it had been berrylium treated. What is it? What does it do to gems? Will it wear off? Are these stones safe to wear? Many Thanks....Ann, USA
Beryllium treatment is a newly developed (last three - four years) extension to the older technology of diffusion. When a gem is diffused, it is heated to a very high temperature in the presence of chemical elements which, when they diffuse into the crystal structure of the gem, give it a certain color. It is used primarily with sapphire and topaz. Older diffusion processes called "surface diffusion", mainly used with blue sapphires, produced a very thin skin of color and as a result the gems weren't durable and the color could wear off or be revealed with chips or scratches. Such gems could not be recut as the color layer would disappear.
The newer process being used with sapphire is called "bulk" or "lattice" diffusion and the light element beryllium which mostly imparts yellow, orange and reddish colors is able to penetrate well into the interior -- in many cases all the way through. Such gems are quite durable and their color can be permanent. There are no safety issues with diffused gems as it has nothing to do with irradiation and there are no chemical dyes on the surface of the gem. The AGTA suggests a gem enhancement code of U for such stones.
Your dealer was honest and forthright in telling you that the stone was enhanced and presumably he/she charged you a price commensurate with a treated, rather than a natural color, stone. In the ethics of gem sales, it's all about disclosure. There's nothing wrong with any kind of enhancement, synthetic or simulant, as long as you know what you are getting and you are paying the appropriate price.
I keep seeing mystic topaz everywhere, but I can't seem to find any information on what it is. Can you tell me what mystic topaz is? How it's made? How it differs from other colored topaz stones? Thank you....Jeri, USA.
"Mystic" topaz is a trade name for a vapor deposition or sputter-coated topaz that shows iridescent colors. The exact nature of the thin metallic coating is proprietary information, but I would guess it contains titanium. There are now several other trademarked brand names of the same thing, such as "Rainbow" topaz, etc. Such stones are fragile and they cannot be re-cut, as to do so removes all or part of the thin color layer. They also should not be used in rings or bracelets that get hard wear as the coating may wear or chip off.
Other artifically colored topazes such as red, blue-green and green have been produced by a surface diffusion process that colors a thin layer in a similar manner to that sometimes used for sapphires. These stones have been heated to near the melting point of the topaz and a coloring element diffuses into the surface layers. These are much more durable than coated stones, but still cannot be re-cut.
You are, I'm sure, familiar with the family of blue topazes which are produced by irradiation and heating of white topaz, such as Swiss, sky, and London blue. These are colored all the way through and the colors are stable.
Finally there are naturally colored topazes such as the yellow, apricot and light orange "precious topazes" which have usually received, at most, simple heat treatment to improve their color toward the pinkish side. There are various brown topazes found in Mexico and other areas whose color, though natural, may fade with exposure to light. There are also natural pink topazes in very light to medium shades. Topaz also occurs naturally and VERY rarely in deep orange (Imperial), red and purple.
I have some vintage crystal necklaces that I had picked up at a church sale. One of them is strung on very fine sterling chain with sterling findings, and friend thought it might be rock cystal, not glass crystal. Is there an easy way to tell the difference between glass crystal and rock crystal (quartz)? thanks!...Yuko, USA
The short answer is YES! There are two simple ways and one not-so-simple one: the first you can do with just a loupe or microscope. Focus on the interior of the stones -- if they are glass they should have at least some bubbles (rounded or oblong inclusions that look hollow) or swirls. If they are quartz they would have more angular solid looking inclusions such as tiny included crystals.
Based on its thermal inertia, glass doesn't feel doesn't feel as cool as most crystalline gems to the touch, although it is not noticeably warm to the touch like plastic. This property is easy to misread, depending on room temperture, the settings the gems are in, and your own level of experience in testing it.
If you scroll down through this "Ask Barbara" page and look for my answer to Carmen in November, I describe how to make a home made polariscope with which you can test your stones. If they stay dark under "crossed filters" as you turn them, they are glass, if they blink from dark to light they are crystalline and therefore possibly quartz.
Dear Barbara, what property is shared by many gems,such as diamonds,rubies,sapphires,emeralds,and topaz?...Cicely, USA
In order to BE a gem, a material has to be a natural mineral or organic substance with substantial beauty, rarity and durability. All of the ones you mention, as gems, share all those characteristics.The first four in your list were once known as "precious" gems, with all other gems, like topaz, being considered "semi-precious" but for most gemologists and jewelers today, that terminology is obsolete. We just call all the species and varieties "gemstones".
In terms of gem characteristics all of the ones you mention come in transparent grades, have fairly high refractive indices, and are of hardness 8 or better. All of them occur in the marketplace in both unenhanced and enhanced forms.
They belong to different chemical groups, though, and have different cyrstallographies as well as quite distinctive optical and physical properties, so I'd have to say that they are really more different than they are alike.
THANK YOU FOR THE VALUABLE INFORMATION REGARDING "MOONSTONE"ON YOUR WEBSITEA. I RECENTLY PURCHASED A MOONSTONE RING, SET IN SILVER AND 14KT GOLD ACCENTS, FROM T J MAX, AND THE STONE IS FACETED. IT IS BLUEISH, WITH PINK HUES EMULATING FROM THE BACK AND SIDES THROUGH THE STONE. I LOOKED AT ANOTHER SITE, AND THEIR MOONSTONE WAS OF HIGH QUALITY, AND EACH READ AS AUTHENTIC MOONSTONE, AND I COULD SEE THAT THEIR PIECES ALL HAD NATURAL INCLUSIONS. THIS STONE SEEMS ALMOST FREE OF INCLUSIONS, AS I HAD A HARD TIME FINDING THEM, ALTHOUGH THEIR WERE SOME, BUT EXTREMELY FEW. IS THIS POSSIBLY A MOONSTONE SYTHENTIC, AND DOES IT EXIST? THE RING WAS $59.99, BUT THE COMPARE PRICE IS $85.00. COULD YOU PLEASE HELP ME TO UNDERSTAND IF IT MAY BE "REAL"?...Alisa, USA
...AFTER EMAILING YOU, I DID MY OWN INVESTIGATING, AND FOUND A STONE CALLED "OPALITE" ON EBAY, AND OTHER SITES. THE RING I PURCHASED LOOKS IDENTICAL TO THIS, AND MAYBE YOU COULD JUST SHED ALITTLE MORE LIGHT WITH YOUR KNOWLEDGE. I THINK I ANSWERED MY OWN QUESTION. THIS MATERIAL IS BEING USED TO PASS OFF AS "MOONSTONE". UNBELIEVABLE! ...Alisa, USA
In both my roles: as a gem dealer and as a gemology teacher, I often get questions about moonstone, which is a name used in a variety of correct and incorrect ways in the general marketplace. You have already figured out that the piece you bought isn't really what gemologists call moonstone--and that was clever detective work on your part! ;-)
"Opalite" has a long history of use in jewelry, going back at least as far as the Victorian Era. It's a type of semi-transparent glass that is made in such a way as to be slightly hazy and iridescent and therefore looks something like some types of opal. It is also marketed (in some very upscale catalogues) under the name "sea opal".
I'm sorry you had the experience of finding out that what you paid for, isn't what you got, but to be honest, it happens to all of us (no matter how much you learn about gemology) -- as long as you think the piece you got is pretty and you enjoy wearing it, at least it isn't a total loss.
I hope you'll continue to visit my site and read the essays, and that you'll look for good gemology books (like Cally Hall's Smithsonian Handbook of Gemstones). Learning more won't protect you 100% against fraud and misrepresentation, but it will make you a more sophisticated buyer and will certainly increase your enjoyment and appreciation of gemstones.
On a travel show they showed a place, I think in Pennsylvania, where one could dig (for a fee) for semi precious gems. They also had many places to pan for gold (for a fee). Do you know where I could find more information on these places?...Dick, USA.
My first thought would be for you to go to a local rock club meeting -- if you don't know of one, contact the Chambers of Commerce of cities in your area. They maintain lists and contact numbers for all sorts of clubs and interest groups. If you find such a group, they would know of any opportunities in your area, and may even lead field trips there.
Another approach would be to start subscribing to, or reading, rock hobby magazines, like Lapidary Journal which often have quite detailed information on fee digging and panning sites. A trip to the website and a thorough exploration of the various links and archives may yield such a list. http://www.lapidaryjournal.com/
Finally, if neither of those approaches "pans out" contact your and surrounding States' tourism bureaus to see if any such sites are within travelling distance.
I have a green/brown colored stone that looks similar to smokey quartz but when held up to the light it has flashes of red,green,blue, orange. Without seeing the stone would you have an idea where to look to compare?...Marcia, USA.
There are two main possibilities that could account for the appearance of your stone. It could be pleochroic or it may be highly dispersive.
Pleochroism is the case where you observe different colors in a gem as you twist and turn it different directions. Each axis of the crystal produces a different color. The only relatively common brownish stone with this characteristic is Andalusite.
Because, you say you see red, green, blue, etc, the stone is more likely to be showing dispersion. This characteristic of some gem species causes the white light that enters it to break up into spectral (rainbow) colors. Diamond shows this attribute strongly which is usually referred to as "fire". Dispersion usually only shows itself in very light colored stones, but there are some exceptions. The brown-green stones which are good candidates for high and visible dispersion are: sphene, sphalerite, perhaps Mali garnet, and, of course, brown diamonds.
Except for brown diamonds I have pictures of all the possibilities on my website that you can look at -- trouble is though, dispersion is hard to capture with the camera. Just enter the species, "sphene", for example, in the search box on the homepage.
Also, you can go to the gem of the month archive read my essay on dispersion (here's a link) to find out more.
One thing is for sure -- your gem is NOT smokey quartz as this variety shows neither distinct pleochroism nor dispersion.
Thanks for the valuable information in your essay about faceting. I am a CPA but may like to have a successful career in faceting. Irrespective of what I do, I want to produce the best, top quality products and services. I believe this characteristic would be beneficial in the faceting process. Can one make a living doing this? The question leads one to reflect on many important life-decision issues. What can one earn doing faceting on a full-time basis? I need some rock-solid information and sources on this aspect of faceting. Your help will be greatly appreciated....Ron, USA.
Perhaps 15 years ago or so I could have been more encouraging to you in regards to becoming a fulltime, professional facetor. The people I know who DO make their living at it, at present, usually combine faceting with other related activities like jewelry design and manufacture or selling gem rough in order to put together a liveable income. With the exception of some "superstars" of the faceting world whose creations (deservedly) sell at a premium to designers and collectors, most facetors make quite modest amounts from their craft. I'm sure there are one or two out there who would prove me wrong, but I know of no one who makes a"full time living wage" from faceting. I do know many, though, who supplement their "day job" income with profits from their faceting hobby, or use it to provide extra money during retirement.
Years ago, the custom faceted gemstone was a great rarity and the vast majority of gems on the market were native or commercial cut. This is becoming less and less true as cutting houses in Thailand and China and other areas convert to modern style equipment and with increased use of computer controlled robotic cutting machines. Such firms are producing decent looking commercial quality stones, from nice looking commercial grade rough at a VERY low price.
As a CPA you must be quite familiar with the difficulty American artisans or workers, in any field, have competing with foreign labor or sophisticated mechanization. The only arena where folks such as you and I still have little competition is in the production of extremely high quality stones, rare or unusual materials, and non-traditional shapes and sizes.
As an example, do an internet search on "8 x 10 mm amethyst oval" and see what such goods sell for, now consider that your yield from rough is going to be approximately 20% and it will take you probably 2-3 hours (once you become proficient) to produce the stone.
I don't mean to be discouraging, but at best I see it as a hobby that can help pay for itself.
I recently came across these two stone descriptions... any comments?: Paraiba Indicolite Tourmaline, Merelani Tsavorite Garnet....Julia, MA.
You don't say where you found the descriptions, but they could mean a couple of things. In gemology, place names can mean just that, but they also have a way of evolving into color names over time. Likewise, trade names tend to of lose their "quotes" which indicate the trade name status as they pass from dealer to dealer.
Paraiba, of course, is a place location in Brazil, the mine site that produced the stunning copper containing super-saturated tourmalines of the same name. To my knowledge, production of that mine is essentially exhausted and has been for some time. Other copper containing blue and green tourmalines have been found in Africa, but, at least to my eye, they haven't the same punch. They are occasionally offered as African "Paraibas" by legitimate dealers and as true Paraibas by others. Very little regulation of trade names exists,so it is buyer beware for sure.
A similar situation exists with the term Padparasha which purists (like me) insist can only be used for Asian-origin sapphires, but which is often applied to African stones that approach the same color.
Any blue or substantially bluish green tourmaline can be legitimately be called indicolite, though, as that is an established gemological variety name.
As far as the term, "Merelani", that is one of the mine areas for Tsavorite, but it often produces stones too light in tone to be officially called Tsavorite, and they sometimes go under the trade name of "Merelani Mint" garnets. In this case your description could be of a very light color stone, or it could just be indicating the mine if it is in the Tsavorite color range. This is the essence of the problem with trade names -- you can't tell just from the name exactly what you've got.
Is there a diamond called a Brilliant Diamond? IF so, is this a real or fake Diamond?...Brendy, US
As far as I know, unless someone has recently introduced this as a trade name, the term "brilliant" in reference to a diamond means "round brilliant", one which is cut in a round shape and has 58 facets. Sometimes the term "brilliant" is used alone instead of the longer, "round brilliant".
Some diamond simulants like "Diamonique" (cubic zirconia) use a form of the word diamond as their trade name, but I have not heard "Brilliant Diamond" used in that way.
I have been collecting and cutting fire agate for a number of years and have recently seen several spectacular specimens (under 40 carats) being sold for about $200.00 per carat. There seems to be almost no demand for anything but the absolute best quality. Do you think that there will ever be any commercial market for medium-to-high grade stones? I still have approx. 600 lbs of rough purchased from the Slaughter Mountain mine from the mid-1990's. Rex....USA
I, personally, have never seen any pieces selling for $200/ct, but I'm not too surprised to hear that you did. In general, the ones I sell go for between $10 and $30 per ct.
One of the issues holding fire agate back as a highly popular gem, is the nature of the material -- it doesn't lend itself to calibrated sizes and so the mass jewelry market isn't interested. Even those buyers who appreciate custom cut cabs and carvings often do not realize the many hours of work it takes to reveal the best in each piece of fire agate. This gem's surface, as you know, must be painstakingly carved to reveal the best colors, and agate is a hard and tough gem which carves slowly. Customers are likely to get "sticker shock" from something with "agate" in its name with higher than expected price per carat. One of the jewelry designers I've purchased from refuses to use the term "fire agate" and sells his pieces as "precious limonite"!
I HAVE A BLACK SET OF PEARLS THAT CONSISTS OF A BRACELET AND NECKLACE, AT LEAST IT LOOKS LIKE BLACK PEARLS TO ME. THEY ARE INDIVIDUALLY KNOTTED, RATHER HEAVY, HIGH LUSTRE AND SMOOTH WITH THE TEETH TEST. WHAT BAFFLES ME IS THAT THEY LOOK AND FEEL REAL. I THOUGHT THEY MIGHT BE HEMATITE BUT COULD NOT FIND ANYTHING ON LINE ABOUT THEM. PLEASE HELP ME DECIDE. THE CLASP IS SILVER COLORED ....RITA
If the pearls are smooth with the tooth test, it usually means that they are imitation pearls. (If you have access to a microscope you could examine the surface for the minute mineral platelets that indicate real pearl -- imitations look and feel smooth).
Don't be surprised that they look so real, today's manufacturers of "faux" pearls do a very good job. The ones which have a weight and feel similar to real pearls are usually made from treated and dyed shell rather than from the less expensive and much previously used plastic. You could rule out hematite by testing with a magnet -- hematite would be slightly to strongly attracted to it, pearls, either faux or real, would not.
I purchased a teardrop cab of what to me looks like gem silica, but was sold to me as Peruvian opal. 24 mm top to bottom 9 (length) x 14 mm wide x 10 mm deep at the highest point of the dome. It is translucent with a very small amount of black/green inclusions. How do I tell the difference between gem silica and Peruvian Opal?...Anjali
Unfortunately there is no reliable way to discriminate these two gems just by sight, as both can have dendritic inclusions and are translucent blue to blue green. Gem silica's blue is usually considerably modified by green tones whereas this is less often true of the opal. If you could send me a picture, it might help.
There are numerous physical and optical differences which can be revealed by testing with gemological instruments. The hardness, refractive index and specific gravities are slightly different between chalcedony (gem silica) and opal, but would require careful testing and can be ambiguous. The surest way would be to subject the piece to a polariscope test, as opal gives an "SR" reaction (dark when turned under crossed filters) and gem silica's reaction is "AGG" (light when turned under crossed filters). Assuming you don't have a polariscope you could seek out a jeweler or gemologist in your area who has one, and have them test it for you. It is also possible to rig up a homemade version of the device from a pair of polaroid sunglasses (see Ask Barbara for November '04, and read my answer to Carmen ) to learn how you would do this, and contact me again if you are interested, so I can describe the procedure and reactions in detail for you.
Having said all that, my first impression is that it is probably opal -- my reasoning is that gem silica is rather scarce, especially in large translucent pieces. If you didn't pay an extremely high price for the piece, then there's a good probability its opal. Most blue opal goes from about $5 to $20 per carat, while gem silica's range is more like $50 - $150 per carat in fine grades.
In my gemstone nugget beads collection I have two types of lemon quartz. One type appears to be a coating over clear quartz in that the surface is ever so slightly cloudy and a bit dull. Whereas, the second nugget type appears to be the result of radiation in that the color saturation is consistent throughout the stone without surface dullness. These stones are superior to what I suspect are dyed nuggets. The quartz used under this 2nd method appears to be alpine crystal quartz which is that beautiful clear non-included material you find used for old time crystal chandelers (sp). I was curious about this: are you seeing both methods, dying and radiation common on the commercial market for the so-called lemon quartz? Is the dying versus radiated treatment going to be a function of the basic quality/ clarity of the clear crystal quartz used in the process? Do you have any information about this. I'm concerned about the stability of the dyed material....Leigh Anne, USA
Hello Leigh Anne,
Thanks for visiting my website and for your question. Without at least a picture, it is hard to determine what you've got, but let me speculate. If your beads are rock crystal quartz which has been dyed, it would most likely be by what is called the quench crackle process. Solid crystalline material is not porous, so it is heated and plunged into cold liquid to create a myriad of tiny fractures into which the dye can penetrate. If this is the case you should be able to see dye concentrations in the cracks with a 10x loupe. It is also possible your beads could be dyed chalcedony which is a type of quartz made up not of a single crystal, but of microscopic interconnected crystals that will take up the dye readily. They could also be glass, plastic, or a variety of synthetics or simulants, so again, I cannot give you any positive conclusions.
In general, today's dyed gems are fairly stable -- modern dyes usually don't wear off or rub off, but some types can fade with long exposure to strong light, be removed by steam or ultrasonic cleaning, or by the use of solvents such as acetone or denatured alcohol. In fact a simple test that will reveal the presence of many dyes is to swab the item with acetone in an inconspicuous area and look for dye transfer. In beads, the drill holes sometimes reveal the true color of the material, but dyeing after drilling can defeat this mode of detection. Under magnification such items might still reveal dye concentrations in surface imperfections, though.
The majority of what I see, that is being called lemon quartz, is irradiated rock crystal, I have seen few dyed pieces, but then I do not handle many beads or nuggets where that process might be more common. The rock crystal which irradiates to that neon yellow color comes from only one area in Brazil, whereas the general outcome from irradiating most colorless quartz is grey-brown smokey quartz. The difference is undoubtedly due to some slight chemical and/or physical difference in the material from that area.
One last point - the term "lemon quartz" is a trade name, not a recognized mineralogical variety name. That means it has no legal meaning and anyone can sell anything they want as lemon quartz. If it isn't really quartz, technically they should put quartz in quotes, but enforcement is minimal on inexpensive gems. Another point to watch out for is use of the word "natural". Legally this word means not synthetic, it doesn't mean unenhanced. So a seller can call the yellow quartz material "natural" and it may still be dyed or irradiated or colored by other means. It's always best to specifically ask whether the material is enhanced.
It sounds like you're a gem detective in the making. There are a number of good books such as "Gem Identification Made Easy " by Antoinette Matlin that you might enjoy.
I recently acquired a large demantoid garnet from Namibia, Africa. It is 3.10 cts. I also purchased a mali garnet from Mali, Western Africa. The dispersion is almost the same in these two stones except the mali garnet is a ligher green. How can I tell if the demantoid is really a demantoid garnet as it has some inclusion but not the horsetail inclusion as does the demantoid garnet from Russia? Is the demantoid from Namibia valuable?...Troy, USA.
Dispersion is an optical property of gems which is much influenced in its expression by the color and cut of the gem. The lighter the color, the greater the clarity, and the higher the crown angles on a cut, the more of the potential for dispersion of a given species will actually be seen. Both Mali and demantoid are dispersive gems, but usually it shows more in Mali garnets because of their greater clarity and lighter color.
Unfortunately, unless you have some gemological equipment or know someone who does, you cannot tell just from looking that a stone is a demantoid. Tests like refractive index, optic character, and specific gravity would be able to give a conclusive identity. True, the Russian specimens have diagnostic inclusions (the horsetails) which confirm their identity -- but the demantoids from Namibia and Arizona in the US, don't have horsetails so other methods must be used in their identification.
In terms of value, if your stone is indeed a demantoid (and eyeclean or better, and well colored) it is reasonably valuable, in the range of one to a few hundred dollars per carat. Only the spectral green Russian stones with horsetails command thousands per carat, though.
Would you please help me to clarify stones that have mostly the same colors like blue topaz, blue zircon, tourmaline,aquamarine, tanzanite...
how to identify these stones?...Samen, Cambodia
Unfortunately gem identification is not a simple matter. Many gems with very different physical and optical properties and values can superficially look similar. Besides being able to discriminate one species from another, there are also synthetics and simulants to consider. Your best bet would be to get a basic gem identification book, such as Antoinette Matlins: "Gem Identification Made Easy". You would also need to invest in some basic gem identification equipment -- at minimum a good loupe, a refractometer, and a dichroscope. A polariscope would be a wise investment as well. Your total costs for these items would be well over $1000.
If you don't have the time or interest to pursue gem identification on your own, the best you can do is to stick with established, reputable dealers who do know how to identify gems. Items purchased on the street, at flea markets, or through newspaper ads have a higher chance of being either unknowingly misidentified or deliberately misrepresented.
Businesses which are members of AGTA for example, are held to exacting standards of ethics and disclosure. Individuals with diplomas in gemology like the FGA, or GG, are also reliable sources. For a very valuable gem, you could insist on a certificate from a recognized laboratory like GIA, EGL or AGTA before purchase.
What would you think if I told you I could get a 2.75 ct flawless custom cut pink tanzanite? What would a person pay for something like that? ... Diane, California.
I have been asked about pink "Tanzanite" several times lately, so I think it's time to have a go at it. I am not aware of any "pink" stones, per se. A small percentage of the normally yellow-brown zoisite rough will heat to green or blue green instead of the usual blue-violet, but to my knowledge pink is not a possible result.
When a stone is cut on the purple-violet axis and its color is very light it could indeed look pink. Before you buy, get a second opinion (other than mine -- nothing I say comes down from the mountain engraved on tablets) -- I'm thinking the "pink" label might be a clever way to market very light material, kind of like "Rose d' France" for extremely light amethyst.
I've discovered that I love freshwater pearls. I've seen beautiful sterling silver rings with pearls that I'd like to buy but I hesitate because of the difficulty I expect to have in cleaning the silver without damaging the pearls. Please tell me what can be used to clean tarnished silver that won't damage the pearls. Thank you so much... Gail, USA.
You aren't alone in the love of freshwater pearls -- they have really hit it big with consumers. And you are correct in being concerned about the cleaning needs of silver versus those of pearl. Here are some tips:
1) Try to purchase your pearls in a silver setting that has been rhodium plated -- a lot of them are. The coating is the same color, but is not susceptible to tarnish. It is true that the coating is thin and will ultimately wear off in spots, but it will not look unsightly when that happens.
2) Wear the piece -- silver that is worn constantly doesn't tarnish as much as that which lanquishes in a drawer or jewelry box, probably either because skin oils form a protective coating or because friction from rubbing, etc. removes forming tarnish. You mention rings, but I wouldn't recommend daily wear for any type of pearl ring, whereas pendants or earrings are another matter. If you do want to wear your pearl ring every day, then just expect that you will have to replace it at some point. With the modest price of freshwater pearls in silver settings you will have an abundant and inexpensive series of choices.
3) When cleaning is necessary, use a soft toothbrush or your fingers and a mild detergent in warm water to clean the pearl -- VERY carefully use the toothbrush with a baking soda paste (mild abrasive) to clean the silver setting. If some of the paste gets on the pearl, rinse it off which will dissolve the little crystals of baking soda, don't wipe it. You can obtain an inexpensive jewelry polishing cloth from your jeweler that has a gentle abrasive embedded which will allow you to shine up your silver ring, although you should still try to avoid the pearls as use it on the silver.
I bought my wife a 1.04 ct. diamond as an engagement ring. Since then she has switched bands and would like to put her birthstone in the other band. I am looking to find a 1ct. amethyst round to set in this ring. Where can I find something like this?... Gary, USA.
The 1.04 carat diamond (I assume, round) if cut with standard proportions would be approximately 6.5 - 6.6 mm in diameter. Diamond is a fairly dense material (specific gravity = 3.52) whereas quartz (amethyst) is quite a bit less dense (specific gravity = 2.66). I mention this because if you bought a one carat round amethyst, cut to diamond proportions, it would be about 7.1 mm in diameter and probably would not fit your setting. So, what you really want to search for is a .80 ct amethyst which will have the desired diameter of approximately 6.5 mm and should fit your setting perfectly. Having said that, there is "good news and bad news" in regards to your lady's request:
The good news is that amethysts are easy to find. The best quality stones are a medium dark purple color sometimes with reddish flashes. An internet search using terms like "6.5 mm, round amethyst, top color" should yield a large number of potential locations where you can purchase a fine stone for a modest price.
The bad news is that amethyst, at hardness 7, is too soft to be worn in a high prong set (Tiffany style) setting all day, every day. If your setting is of this type, and if she plans to put it on and never take it off -- then the amethyst will not wear well enough for such use.
The only gems suitable for such heavy use in rings in exposed settings are those with hardnesses of 8 or higher, and with good toughness: diamonds, sapphires & rubies, chrysoberyls and perhaps spinels qualify. Sapphires and spinels do come in amethyst-purple, but they are rare and expensive, if natural.
Is there a way of looking through a regular magnifying glass or a loupe to distinguish the difference between an aquamarine and a blue topaz?...Annie, Nevada.
Unfortunately there is no sure fire visual way to separate the two. Some folks are under the impression that aqua is always a lighter blue than blue topaz -- but there are some aquas which are quite dark in color, and some pale topazes, so very light color doesn't always mean aqua, and darker color doesn't always mean topaz. And, there is no reliable way to tell an aqua from a topaz with a loupe. There are big physical and optical differences that can be determined with other methods such as using a spectroscope, a refractometer or determining specific gravity, but using a loupe is usually not conclusive.
One visual possibility, though, is a type of inclusion called a "growth tube" which is typical of beryl (aqua) and rarely, if ever. seen in topaz. Not all aquas will show them, though. Growth tubes are straight hollow channels that are usually thicker than rutile needles. Another signal might be the presence of cleavages (straight breaks) on the surface or in the interior of the stone -- topaz is much more prone to cleavages than beryl. All in all though, visual discrimination of these two blue gems is dicey at best.
I have been enjoying looking at your website; it's very informative. I was wondering whether you could help me identify a stone - a friend has brought some from Brazil; she says this one is called "green gold" - she said it was not a type of topaz but was simply referred to as "green gold" - I haven't heard of that before. The color to me looks similar to the stone on your website called Mali garnet. I've attached a picture - sorry for its poor quality due to my scanner. Thanks for any information....Amy, USA.
The first rule of gem identification is "never do a sight ID" -- having said that, I'm reasonably sure your stone is a type of irradiated quartz. The term "green gold" is the English version of the trade name "Oro Verde" commonly used for quartz of this type. Some vendors call it Lemon Quartz. Usually when colorless quartz is irradiated the result is brownish grey smokey quartz, but rough from certain mines has a slightly different chemistry and it comes out this pretty chartreuse color. The process is similar to that used to make blue topaz out of colorless topaz. In Brazil "topazos" means yellow and historically was applied loosely to any yellow stone, be it quartz or topaz, tourmaline or any other. Yellow topaz does come from Brazil but its color is an orangey to brownish to pinkish yellow not the greenish tone in your stone. It is unlikely to be any type of garnet as very little of that gem in any yellow variety originates in S. America.
How can I tell a glass stone from a gemstone? I have a 10X Loupe and three rings the stones of which are questionable. One jeweller told me the stones are real (blue topaz, yellow/brown topaz and amethyst) and another told me they are glass only....Carmen, Alaska.
It is usually pretty easy to spot glass "stones" with a loupe -- first thing is to get good lighting. Gemologists frequently use what is called "darkfield illumination" to examine gems as it makes any inclusions easier to spot. With darkfield, the light enters the gem from the side and the gem is seen against a dark background. You can rig a pretty good simulation of darkfield by using a desk lamp or some other type of light with a shade, tape a strip of black paper right below the shade then hold the gem right under that paper and view it from the side, with your loupe.
First look at the gem's surface, glass stones usually have somewhat rounded facets edges (not like a sharp knife edge). Then turn your attention to the interior -- small rounded gas bubbles and/or swirl marks are signs of glass.
If you can't see enough to make a call on the stones, and if you really want to pursue it, you can make a homemade polariscope. A working model of this expensive piece of gemologist's equipment can be gerry-rigged with a penlight or small flashlight, a widetooth comb and an old pair of polaroid sunglasses -- these will have to be sacrificed so don't use your new Maui Jims!
Remove the lenses from the glasses (they must be polaroid or it won't work). Using the flashlight as a light source and the comb to hold the lenses do the following. (You will either need three hands or helper!) Hold the flashlight between your knees or prop it up so that the light beam goes up, stand the comb up above the light, and put one of the sunglass lenses near the bottom, but above the light. Put the other lens near the top of the comb (the teeth should hold the lens in place). Now adjust the two lenses so that as you look down through the top lens to the bottom one, the least amount of light passes through. Try turning the top lens in different directions until this is accomplished. Now you have your polariscope set up in what is called the "crossed filters" mode. Put one of your gems in between the two filters and slowly twist it in a 360 degree arc. If the gem is doubly refractive like topaz and amethyst, it will blink dark/light/dark/light -- if it is amorphous, like glass, it will stay the same shade of dark no matter how you turn it.
What is a Pyralspite garnet? Is it a special type of garnet or just the whole family of garnets? Thanks...Robert, USA
The garnet family of gem minerals is a group of closely related species which share a common crystal structure and similar chemical formulae.
The quick, first answer to your question is that a "pyralspite" garnet is more than one species and less than the whole group -- it would be any of the three member species of the pyralspite series of species within the garnet group.
To amplify: the generic formula for any garnet is "A"3"B"2Si3012 where the "A" position can be occupied by iron, calcium, manganese or magnesium and the "B" position can be occupied by aluminum, iron, titanium or chromium. The rest of the formula is standard for all and makes every garnet one of the "silicate" gems.
The six most closely related species in this large family are divided into two "series": the pyralspites and the ugrandites
The pryalspites (pyropes, almandites and spessartites) have aluminum in the "B" position and the ugrandites (uvavovite, grossularite and andradites) have calcium in the "A" position.
In addition to these six, there are other species within the garnet group which are either virtually unobtainable or have no "gem" properties. And there are also named varieties like rhodolite and malaya which are often said to be intermediate in composition between various members of the six species gemologically important species.
Most gemologists would agree that very few to no garnets are 100% of one species or another and all of them, in truth, represent mixtures along this "solid solution" series. So, in practice, since chemical composition is so complicated and variable, we usually identify a garnet by color, and refractive index rather than by its chemistry. The one main exception to that might be uvarovite, which has restricted distribution and is the most unique of the six in its properties and characteristics.
When someone says a cut stone is "calibrated", what does that term mean?...King, USA.
Calibrated means cut to a standard size: such as 10 x 8 mm, for example, for an oval or 6 mm for a round. Calibrated sizes are necessary when trying to put stones into pre-manufactured mountings. Stones that aren't calibrated usually require that the commercial mounting be adjusted by a jeweler to fit the stone, or, more likely that a custom mounting must be made for it.
I would like to know how and at what temperature gems are heated to change their color? Thank you...Jim, USA.
The simple answer to your question, is that "it depends" -- for example: heat can be used to darken, to lighten, to change hue, or to remove or to induce certain inclusions. With zircon, different results are obtained with high temperature (1000 degrees Centigrade) versus low temp. (150 degrees C), and with oxidizing versus reducing atmospheres.
My best advice would be to run, not walk, to your nearest bookstore (bricks and mortar or on-line) and get a copy of Kurt Nassau's definitive work on the subject: Gemstone Enhancement: History, Science and State of the Art, 2nd Ed. ISBN # 0 7506 1797 7
Among other things, you'll find a chapter on heat treatments, covering the species which can and can't be treated, temperatures, heating/cooling regimens and atmospheric conditions (reducing/oxidizing) appropriate for various materials from amber to zoisite.
One fairly general point in all heating procedures is that due to thermal expansion rates in a gem and to differences in the rates between those gem minerals and their inclusions, it is best to start with clean rough or cut stones. It is also important to raise and lower the temperature very slowly.
I have a stone (rather large), it is shades of purple at most times and at others it will be a beautiful blue. It will change colors inside or out, warm or cool weather. It is set in a silver ring in a round cut. I have read about color changing stones but not that combo. What might it be?
Also another ring somewhat old, (say at least 60 yrs) has 5 small what I thought were emerald stones, until they were removed to repair the setting. When viewed from bottom side they are red. (?) Thanks 4 help...Jennifer, USA
I'll answer your second question first as it is easier.
I'm 99% sure your green stones are a type of assembled stone called "garnet and glass doublets". Before it was technically possible and economically feasible to make synthetic stones our predecessors had to use their ingenuity and it really shows in these creations. The bottom and most of the top of the piece is made of green glass, with a thin layer of red garnet glued to the top. The thin garnet layer adds no color when seen face up, but gives the stone durability and even some natural looking inclusions to reassure an owner looking at it with a loupe. Once set in a mounting they are very hard to detect, and very attractive looking --the simulation is that good. They are usually detectable with magnification or as in your case when unmounted and turned upside down. At present these are antique curiosities, actually kind of cool -- enjoy them for what they are. :-)
The blue/purple stone could be a case of true color change or the stone could just be extremely pleochroic like iolite or Tanzanite. If it changes completely in different light sources then it is color change, but if the change is more based on what direction you turn the stone, and occurs in a place with multiple light sources (like a room lit with a mix of incandescent and fluorescent lights) it could be merely pleochroic.
Having said that, I'll go out on a limb and say that your stone is most likely a type of synthetic corundum (sapphire) sold under the name "Alexandrium" -- alternately it could be one of the newer types of man-made color change glass which show a blue to purple change.
A large stone with a very distinct color change would be worth a great deal of money, and probably wouldn't be set in a silver ring.
What is a Hydrogrossular garnet? Is it real or is it man made? Thanks. ....R. Black, USA
Hydrogrossular garnet is a mineral species belonging to the garnet group of minerals. In general pieces are translucent green with spots and markings but also occur in opaque forms and in shades through grey to pink. They are almost always cut as cabochons or carved Most specimens come from South. Africa. The resemblance of the green type to jade has led to the misnomer "Transvaal Jade" which has been used in commerce. Perhaps this is what gave you the impression there was something "not real" about it.
I am a new gem collector. I have been told that I should sell some of my Tanzanite high and make money (to buy other gems). If so, where would I sell them? Are there buyers out there for regular people?...Vicki, USA
Just to give you a general background against which to gauge my remarks, let me say that I have never been an advocate of "investment" in gems. Too many factors, such as new finds, changes in government policies and changes in fashion trends make it entirely too risky. I own hundreds of gems in my personal collection, but I bought them all because I found them interesting or beautiful, rather than with any expectation they might appreciate in value.
As far as your Tanzanite question, the main factors to consider are:
1) What did you pay for the stones? 2) What is their size, color and quality -- tiny differences in Tanzanite color make big differences in the price, and price per carat increases exponentially with size in this gem 3) What are retail and wholesale Tanzanite prices now and what will they be in the future?
Unfortunately, there is no regular marketplace through which a private collector can sell their gems -- instead, those who wish or need to sell gems:
Try to sell to a jeweler
Put a classified ad in a newspaper or magazine
Try an online auction
Any of these situations, is very much a "buyers" market, and it would be difficult to sell even the best gems for a good price. Gem buyers generally have established, wholesale sources and (I'm assuming your original purchase was retail). So even if prices have gone up, you will be competing against these wholesalers who can almost always offer the lowest prices. I'm sorry to sound discouraging -- it may be theoretically true that you bought cheaper than the current retail selling price, but for you to translate that into a profitable sale is, sadly, rather unlikely.
I've decided that I need a loupe, and did some research. There are more than plenty of 10x triplets to choose from, so I am little bit at a loss and decided to seek your advice. ...Julia, Boston
Well, you've narrowed down the job quite a bit by deciding you want a triplet loupe, which is the best way to go, even if it adds to the cost. Triplet loupes have three lenses, each of which has been specially ground so that as a group they correct for the chromatic and optical distortion of any single lens. Beyond that, you want to consider size, magnification and packaging.
Size -- a bigger loupe gives you a wider field of view (probably not necessary for most gems) and adds to the cost considerably.
Magnification -- the higher the magnification the shorter the focal length and the closer the lens must be held to the gem. The standard 10x loupe will focus at 1" from the object. It's hard enough to get used to that -- so don't be tempted to go for a 15X or 20X model which is very tricky to focus and must be practically touching the gem. Besides, 10x is the standard even for the picky art of diamond grading.
Packaging -- the housing: plastic, metal: silver, black, etc. Make your choice based on the weight you prefer, what kind of "wear" you expect to give it, and what appeals to you appearance-wise. Some recommend the black coating as minimizing reflections, but I have both kinds, and never have noticed a difference.
(Now to be practical -- the only place I actually use my 10x loupe is when I go to gem shows or to visit a cutter) -- for all my routine grading in the studio I use a 10x Darkfield loupe. It consists of a triplet loupe within a housing which fits over a standard "Maglite" style flashlite. This set up baffles the light and directs it through the side of the gem. The stone, then, is seen against a dark background. The side lighting reflects strongly from any inclusions or interior features (increases their apparent "relief") so that they jump right out at you. Prices can be high @ $200 for the model I have, but I recently saw a couple of less expensive models in the Riogrande catalog that look good.
Bottom line recommendation : get the least expensive 10x triplet loupe you can find from a known manufacturer (German, Japanese and American companies all have good reputations for precision lens making), in a moderately small size, with either a black or silver metal housing -- and don't forget to get a good pair of, preferably locking, gem tweezers.
What colored gemstones are suitable for daily wear, such as in a wedding ring? ..."S", N. Carolina
I'm glad you asked that question! Many gems are promoted for use in rings without adequate consideration of their durability.
In general, I would recommend only gems of hardness 8.5, and above, for constant daily wear in a ring or bracelet. That pretty much restricts the colored stone choices to chrysoberyl and corundum (sapphire and ruby). It's important to note, though, that not all specimens of a species with a given hardness are equally tough. Inclusions in a gem, especially fractures which reach the surface can dramatically reduce a gem's durability. This is notably the case with emeralds which are usually considerably more fragile than their published hardness of 7.5 - 8 would imply, due to such internal fractures.
Before I get a flood of mail along the lines of: "well, I've got an aquamarine ring (hardness 7.5 - 8) that I wear every day and its fine" or "my Aunt had a ruby ring and the gem broke", let me also say that each individual situation is different: how "protective" a setting is, makes a big difference. A bezel setting, or one in which the colored gem surface is recessed below the metalwork or below diamond accents, can make a less durable gem more useable. The gemstone's shape can make a difference -- pear shaped or marquis gems with sharp points are more vulnerable than a round, cushion or cut corner shape. (The "emerald cut", a cut corner rectangle, got it's name as it was used so frequently to improve the durability of emerald gems). Other significant factors are the lifestyle, occupation and habits of the individual who is wearing the ring: some folks are just hard on jewelry, others less so.
When thinking about rings that aren't worn 24/7, the field opens up greatly. Certainly any gem with hardness 7 and above is a candidate. And as demonstrated by the common use in rings of some pretty fragile gems (pearls and opal come to mind), with sufficient care, most commonly available gems can be used successfully in occasional wear rings.
I purchased a Eudialyte necklace from you. I absolutely love it as I have with everything I have purchased from you. I was on the "Mineralogy Database" the other day and it said that Eudialyte is mildly radioactive. Does this pose a health concern that you are aware of? ...Lucinda, New York.
Eudialyte is classed as you mentioned: "mildly" radioactive. The estimated radiation dosage from a one gram piece (5 ct) held in the hand for one hour is .002 mREM. The allowable dose for an adult is 50,000 mREM per year - (body) and 15,000 mREM per year - (eyes). To put this in perspective: There are 8766 hours in a year. If you wore a 5 ct. stone continuously for a year, your radiation dose would be .002 mREM x 8766 hours/year = 17.53 mREM per year. This is .035% of the allowable dose for the body and .116% of the dose for your eyes.
The unavoidable sources of natural background radiation from the soil androcks, radiation from space, in foods, etc. and the elective forms such as medical radioisotope studies and diagnostic procedures dwarf those figures. Although it is wise to ask such a question, and there are worries about improperly "cooled" irradiated gems which could be a problem, and some natural minerals with radiation levels that should be avoided -- eudialyte can be enjoyed without concern. :-)
I found part of a string of pearls on the street. I don't know whether they are cultured or "real" but they are one or the other as they are ever so slightly out of round, and are ever so slightly rough. They appear smooth but really are not. There is no layer of finish on them. They were double knotted and the clasp is white gold and appears to be vintage. Where can I get a value for the individual pearls? Thanks... Jackie, USA.
Thanks for visiting my website and for your question. Once my son found an 18k gold charm bracelet in a parking lot -- so it's amazing what you can find if you keep your eyes open! Let me clarify some basic terminology first: there are essentially no more natural pearls -- most of the ones which were harvested in previous centuries are in the state treasury of Iran or in the hands of private collectors. Today's "real" pearl is a cultured pearl as opposed to pearl simulants euphemistically called "faux" pearls. A simple test, which can often discriminate real from faux, is the tooth test. Rub the surface of the pearl across your front teeth -- if it feels smooth then it's probably a simulant, whereas a slightly rough feeling means it's most likely cultured. Your saying that they were on 14k gold and individually knotted leads me, also, to think that they are probably cultured. The slight out of roundness isn't always an indication that they are freshwater pearls, but could be. When you say they have "no layer of finish", if you mean that have no nacre or slightly iridescent "orient" -- then they are probably damaged and not worth anything. If, on the other hand, you mean there is no layer of lacquer or waxy sealant, then, again, it would point to cultured rather than simulant.
What sets value in individual pearls includes a variety of factors --
1) color and orient -- body color can be silvery white, creamy white, through all shades of yellowish, pinkish and peachy -- or can be dyed virtually any color in the rainbow. Natural is always worth more than dyed. You can sometimes detect dye by looking at the drill hole with a microscope to see the bead's true color. Orient (overtones of slight iridescence) brings more value the stronger it is.
2) roundness -- in general the rounder the better
3) size -- bigger is worth more.
4) salt or freshwater origin -- saltwater pearls are usually worth more than freshwater pearls of any given size and color.
You might want to take them to a custom jeweler in your area for a quick opinion, but to get an actual identification or evaluation from an appraiser/gemologist would be expensive.
I was looking at gemstone pendants and came across an item identified as Fossil Palm. However, this item has a pattern of yellowish tan swirls on dark brown and is unlike the pinpoint pattern described for palm wood. Could this be another type of fossilized gemstone?...Annie, USA.
I could probably tell you more accurately if you could send me the URL so I could take a look at the pendant, but I can tell you, sight unseen, that it certainly could be palm wood.
What form the pattern takes in a fossilized piece of wood is dependent on a large number of factors such as the exact species and tissue of the wood, the mineral which replaces it, and the rate, completeness and conditions under which the petrifaction occurs. For example, I have a specimen of fossilized palm root in the new June collection and its pattern and colors look quite different than the typical "dotted" palm wood pattern. Roots have a different internal structure and growth form than ordinary wood. Likewise, another piece in inventory is a fossilzed palm wood burl with its own distinctive pattern.
Another major factor that enters in, is how the gem was oriented when cutting it from the rough. In a piece of palm wood, the water carrying structures in the wood are like very long thin straws -- picture taking a bundle of straws in your hand and cutting them in various ways. If you cut them in cross section, you'll get a bunch of circles, but if you do it at an angle or lengthwise the shapes produced will look very different. So it is with cutting fossil woods and other plant structures. Since many people find the dotted pattern of palmwood attractive and, therefore, such pieces are highly saleable, gemstones are generally cut to display that pattern if at all possible.
I have always wondered what the word "grossular" means when describing a grossular garnet--and why are these stones usually green?...Lauren, Massachusetts
The name is from the Greek "grossularia" or gooseberry. This is a reference to the light yellow-green color of the first type of grossular garnet discovered (an opaque, non-gem type). Although the more valuable and available members of this group are green, they are not really the most common, color-wise. The colors range from the colorless of pure grossular (quite valuable to collectors) to yellow, pink, orange, brown and black, each created by the presence of various chemical elements. Some other well known members of this same group are "hessonites -- orangey brown grossulars and Tsavorites -- medium to dark green grossulars.
Grossular garnets often have a particular inclusion which is an identifying characteristic: called "treacle". Under a microscope, swirled patterns are created by tiny included crystals, generally diopside. Hardness ranges from 6.5 -7.5 with an average specific gravity of 3.6. Generally it forms by contact metamorphism and only in localized deposits. Major sources for grossular garnet are Sri Lanka, Pakistan, Russia, Canada, USA, Mexico, Africa, Australia and Brazil.
Hydrogrossular garnet, an opaque to translucent green to pink closely related gemstone, has a long history in the gem trade usually under the name of "Transvaal jade".
Garnets belong to the isometric crystal system and commonly grow in a distinctive well developed crystal form known as a dodecahedron (triangular-shaped faces). Natural garnets are a complex "solid solution series" of gemstones. This means that the various species share a crystal structure and an infinitely grading series of generally similar chemical formulas. Gemologists divide them into the calcium bearing "ugrandites", named after the initial letters of the three calcium species: uvarovite, grossular, and andradite, and the calcium-free pyralspites, named after: pyrope, almandine, and Spessartite. Aluminum, iron, and chromium substitute freely in the ugrandites whereas iron, magnesium, and manganese substitute readily for one another in the pyralspites. All gradations between the pure species are possible and as most gemologists do not have at their disposal a means for precisely determining the chemical composition of a garnet, we rely on color and refractive index for classification.
I just went to your web-site in search of a little help with a ring I inherited from my grandmother. It is a child's ring with what was told to me to be, a ruby. However, I had it appraised in 1985 by a town jeweler. He told me that it was glass. I understand that in the 1900's many fabricated rubies were circulating at the time. My grandmother's father gave her the ring as a child. He was a mine-inspector during the turn of the century. Do you think I should have a gemologist take a look at this ring or was the appraisal sufficient from the jeweler? The setting was appraised at $250.00. ...Suzanne, USA
It would be very easy for a gemologist to tell whether the piece is glass or not -- a polariscope test absolutely discriminates amorphous substances like glass from crystalline materials like ruby. The specific gravity and refractive index tests could be added, if the material is crystalline, to discriminate ruby from other red gems like garnet or spinel. If it is a ruby, determining whether it is a synthetic ruby or a natural one is a bit more difficult. Given the age of the piece, if it is synthetic, it would be a "flame fusion" type which is generally the easiest to discriminate from natural. A synthetic stone would not add any value beyond that already determined for the setting, but if it's natural, the value should go up proportionately based on the size of the stone and its quality. Whether sending it to a gemological laboratory is worth doing, which would cost you approximately $75-$100, depends on how badly you want to know what the stone is, and whether you intend to sell it, or want to insure it.
Cuprite/malachite is a very striking (red and green) colour contrast, but would the cuprite oxidise over time and become more greenish? ...Denise, England
The short answer to the cuprite question is no, it won't change. Cuprite is Cu2O, technically cuprous oxide, and it is already as oxidized as it will get in atmospheric air, so the color is stable. Were you to heat it in a furnace with a reducing atmosphere, or to subject it to acids or bases that might be a different story.
To add some additional, related, information: Copper normally produces green colors when present in a mineral in amounts up to 5%, over which, the color darkens to black. If you've looked at a lot gems of copper-containing mineral mixtures, most of them have some black areas as a result. Metallic copper and metal alloys which contain copper, often acquire a lovely green "patina". This is caused by green copper salts, which are combinations of the metal copper and various other chemicals. Examples include copper sulfate and copper acetate. The green color of our Statue of Liberty is the outcome of the exposure of its copper to the environment, with its various chemical contaminants, which results in the production of the mixture of green salts of its patina. The same thing applies when a green mark is left on your skin from wearing jewelry made of some copper containing metals. We constantly release acidic chemicals from our bodies in the our sweat which cause such metals to form the green salts, which easily rub off. At one time, a common home-made source of green pigment for artists was the patina scrapings from copper that had been exposed to acid vapors.
"I've been a lurker on your website for quite some time and I'm wondering about some of the wonderful blue and blue green gems I've seen there, like Azurite/Malachite. What is their hardness? Are they suitable for jewelry use?" ...Mary, New York
Although azurite and malachite are both fairly soft minerals, in Nature they are often combined in various proportions with quartz which has a hardness of 7. In general, the harder the material, the shinier the polish that can be obtained. (Polish also depends, of course, on the skill of the cutter). A simple rule of thumb, then, would be, the higher the polish on one of these mixtures, the more quartz and the harder the gem, and so, the more usable it is in jewelry. Soft minerals like chrysocolla, and cuprite also sometimes occur in attractive gemstones that have a fairly high proportion of quartz in their makeup.
On the ACS site such stones are labeled with the (J/D) jewelry use code, which means that they can be used for jewelry purposes, but protective settings and care in setting and wearing are good ideas. Earrings, pendants and brooches made with stones of this type would be quite safe. Daily wear rings, bracelets and belt buckles would be very risky, but occasional wear of such pieces would most likely be OK.
"I'm a beginner in the gem hobby. Can you recommend a good book?" ...Scott, Florida
I get that question frequently, and I usually recommend The Eye Witness Handbook of Gemstones, by Cally Hall. It has wonderful photos and illustrations and highly readable text. Each page is devoted to one species or variety of gemstone, and although detailed gemological information is there, it is unobtrusive. Most entries have photos of the gem as rough, cut specimens, and set in jewelry. There are notes on lore, history and major world sources. This book is a delight for the more advanced gem lover, as well as the beginner -- so you won't "outgrow" it. Best of all, it's only about $20 and is widely available from internet sellers such as Amazon.com, and "bricks and mortar" chains like B. Dalton.
"What do you think of the gems and jewelry sold on TV on the shopping channels?" ...Jean, Ohio
(The first thing I'd better say in answering this question, is that you should "consider the source" -- they are, afterall, my competitors, secondly, I'm giving you my opinion not an unbiased, factual analysis.) That being said, here goes:
There are a growing number of these venues, some of which broadcast 24 hours a day, and others which operate more like info-mercials or auctions. I think, in general, they have had an overall positive effect on the colored stone marketplace. People watch their shows and are introduced to a wide variety of gem species that are not common in jewelry stores and catalogs. In my view, any development which promotes increased exposure to the diversity of colored gemstones is "a good thing".
On the other hand, I feel that in their attempt to appeal to a very wide, often gemologically naive, audience, and to sell mass quantities of their items, much of what they say about their merchandise is misleading. For example, two terms that are virtually always misused on such shows are "rare" and "natural". To call gemstones which they sell in multiples of thousands of pieces, over and over in the course of time "rare" is, in my opinion, a misuse of the term. Likewise, the term "natural" is frequently used to imply, that a gem has not been enhanced -- for example, the vast majority of the jade sold on these shows is dyed, but they repeatedly refer to it as natural. True, it is natural jade as opposed to a synthetic or imitation, but it has been bleached and then dyed to produce totally "unnatural" colors. There's nothing wrong with selling dyed jade (there is a huge market for it) as long as it is clear to the customer that it has been dyed.
The shopping channels operate, as I do, under the guidelines published by the Federal Trade Commission which sets rules for advertising. They employ a legal staff to make sure that they, at least technically, comply with the letter of the law, but I feel they frequently circumvent the "spirit" of the law. As a member of AGTA (The American Gem Trade Association, which publishes the accepted industry guidelines for disclosure of enhancements), and from my own personal convictions, I believe sellers should make the maximum disclosure on the goods they sell, (not the minimum technically required by law).
As far as the quality of their merchandise, I have no quibble with it. They sell what would be called "commercial" quality goods. That's not a slam, as 99% of the gems in the marketplace including those in mall jewelry stores and mail order catalogs, are in that category. With their huge buying power they can offer you about the best price you are going to find on such items. If, on the other hand, you're looking for something more in the range of "gem quality" (AAA color, custom cut, etc.) you won't find it on TV. (Even though they use that phrase liberally.) Such pieces are truly rare and there is no way they can be provided in calibrated sizes, and matching colors for hundreds to thousands of jewelry pieces. The jewelry pieces they offer are also a good bargain, for mass produced items, though settings tend to be hollowed out, or made of light gauge material. If what you want is a limited edition, or one-of-a-kind custom design, you should look elsewhere.
To sum up: they cut a few corners, ethically, on disclosure of treatments and exaggeration of rarity, but offer excellent bargains for the type of goods they sell.