Dear Barbara,
What's the difference between a gem, i.e., a diamond, being "heat treated" versus one that's been "irradiated"?...Veronica, USA.
Hello Veronica:
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.
Dear Barbara,
Hi! I am from the Philippines. May I know how to detect a "Diamond Hybrid" against real diamond gemstone. Thank you....Josephine, The Philippines
Hello Josephine:
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.
Dear Barbara,
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.
Hello Smadar:
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.
http://www.bwsmigel.info/Lesson5/DE.Magnification.html
http://www.bwsmigel.info/Lesson10/DE.Gem.Formation.html
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.
Dear Barbara,
Hi there. In regards to your Gemology course: do you offer a summer short course, or any short courses for that matter?... Nathan, USA.
Hello Nathan:
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.
Dear Barbara,
Could you please tell me what is the rarest gemstone? My friend said it was an emerald...Monica, England
Hello Monica:
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
Dear Barbara,
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
Hello Betty,
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.
Dear Barbara,
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
Hello Douglas,
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.
Dear Barbara,
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
Hello Candace,
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.
Dear Barbara,
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
Hello Jim:
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.
Dear Barbara,
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.
Hello Ann,
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.
Dear Barbara,
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.
Hello Richard,
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.
Dear Barbara,
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
Hello Shirley,
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.
http://www.acstones.com/gemofmonth/2007/gemofmonth.04.07.html
Dear Barbara,
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
Hello Darlene,
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.
Dear Barbara,
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
Hello Cindy,
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.
Dear Barbara,
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.
Hello Tamara,
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.
Dear Barbara,
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
Hello Deepti,
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.
Dear Barbara,
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
Hello Jeanette:
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.
Dear Barbara,
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
Hello Melissa:
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.
Dear Barbara,
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.
http://www.acstones.com/gemofmonth/2005/gemofmonth.02.05.html
Dear Barbara,
Hi! Can colorless topaz test positive as being a diamond, with the copper probe?... Linda, Australia.
Hello Linda:
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.
Dear Barbara,
What generic product can I use to clean a pair of mystic topaz white gold earrings?...Linda, US
Hello Linda:
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.
Dear Barbara,
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.
Hello Emma:
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!
Dear Barbara,
Could you give me any information on iris or rainbow rhinestones..or what rainbow quartz looks
like?...Brenda, Florida
Hello Brenda:
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.
Dear Barbara,
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
Hello Elaine:
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.
Dear Barbara,
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
Hello Christine:
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.
Dear Barbara,
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.
Hello Patty:
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.
Dear Barbara,
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.
Hello Gina:
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.
Dear Barbara,
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.
Hello Shirley:
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.
Dear Barbara,
What is Sunrise topaz? Is it a natural stone or is it colorless topaz which has been heat-treated or dyed? ...Tamara, USA.
Hello Tamara:
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.
Dear Barbara,
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.
Hello Emily:
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.
Dear Barbara,
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.
Hello Gaylene:
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.
Dear Barbara,
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.
Hello Joseph:
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.
http://www.bwsmigel.info/Lesson5/DE.Magnification.html
http://www.bwsmigel.info/GEOL.115.ESSAYS/Gemology.Included.Quartz.html
Dear Barbara,
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
Hello Cathryn:
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".
Dear Barbara,
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
Hello Teresa:
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.html
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.
http://www.acstones.com/gemofmonth/2004/gemofmonth8.04.html
Dear Barbara,
I just love smokey Topaz and Quartz. How do you tell the difference, and which one is better/more valuable/stronger??...Rochelle, USA
Hello Rochelle:
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.
Dear Barbara,
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
Hello Sharon:
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 loupe
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.
Dichroscope (GIA's)
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
Dear Barbara,
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.
Hello Kasey:
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.
Dear Barbara,
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
Hello Nisha:
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.
Dear Barbara,
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
Hello Margie:
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?).
Dear Barbara,
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.
Hello Peter:
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,[1] What is 10x on the microscope? [2] And if the stone I have is very smooth is it glass? [3] 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.
Dear Barbara,
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
Hello Christoper:
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
Dear Barbara,
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
Hello Tammie:
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.
Dear Barbara,
I have a ruby ring that is over 60 yrs old. How do I tell if the ruby is real?..Angela, USA
Hello Angela:
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.
Dear Barbara,
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.
Hello Deborah:
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.
Dear Barbara,
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.
Hello Mike:
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)
Barbara,
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.
Dear Barbara,
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.
Dear Barbara,
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.
Dear Barbara,
Hi, I am new to the "gem world", and would like to know what "AB Quality" means. Any help would be appreciated...Jennifer, Oregon
Hello Jennifer:
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.
Hello Jan:
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)
Dear Barbara,
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.
Hello Diane:
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.
Dear Barbara,
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
Hello Jan,
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.
Dear Barbara,
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, ?
Hello 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. :-)
Dear Barbara,
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.
Hello Jena,
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.
Dear Barbara,
What is hessonite garnet and how valuable is the stone?...Pam
Hello 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.
Dear Barbara,
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
Hello Patricia,
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....
Dear Barbara,
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
Hello Stephanie,
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.
Dear Barbara:
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
Helo Sean,
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).
Dear Barbara,
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
Hello Ryan,
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.
Dear Barbara,
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
Hello Kathleen,
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.
Dear Barbara,
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
Hello Kimberly,
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. :-)
Dear Barbara,
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
Hello Jim,
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.
Dear Barbara,
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
Hello Gail,
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.
Dear Barbara,
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
Hello Carlos,
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.
Dear Barbara,
Have you ever heard of a Namibian tourmaline, blue-green, called neuchwauben?...Peggy, USA
Hello Peggy,
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.
Dear Barbara,
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.
topaz
natural
emerald, faceted
length 24.69mm; width 19.95mm; depth 11.45mm
depth % 57.4
clarity:fI
primary color: blue
secondary color: green
symmetry: good
color intensity: medium
transparency: transparent
tone: 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
Hello Wendy,
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.
Dear Barbara,
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.
Hello Sujatha,
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.
Dear Barbara,
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 emeral