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 the rainbow quartz looks
like...Brenda, Florida
Hello Brenda:
I'm not sure of that terminology, so I will give you my best guesses. 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 material 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. 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:
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 for 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 a 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 (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 skin deep color, but they are all just trade names. The treatment is not simple heating nor is it dyeing. Under incredibly high temperatures the topaz rough (probably colorless) has 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 as long as the diffusion is disclosed to the buyer and the price is appropriate. In this case the appropriate price is just slightly higher than that of white topaz. To answer your question, then, yes, it is natural (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 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.
http://www.bwsmigel.info/GEOL.115.ESSAYS/Gemology.Unusual.Organics.html
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 emerald ring, however several people have told me that emeralds are fragile, and not suitable as an engagement ring. Is this true? ....Pam, UK
Hello Pam:
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.
Dear Barbara,
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.
Hello Lynn,
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.
Dear Barbara,
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
Hello Lanette:
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! :-)
Dear Barbara,
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
Hello Diane,
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.
Dear Barbara,
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
Hello Ivan,
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. :-)
Dear Barbara,
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
Hello Susan,
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.)
Dear Barbara,
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.
Hello Lauren,
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.
Dear Barbara,
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.
Hello Terry,
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.
Dear Barbara,
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
Hello Jimmy,
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).
Dear Barbara,
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
Hello Diane,
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.
Dear Barbara,
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.
Hello Kim,
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.
http://www.acstones.com/gemofmonth/2006/gemofmonth.01.06.html
In the short run it is best to buy from established firms that offer a money-back guarantee.
Dear Barbara,
What is the difference between beryl and chrysoberyl? And if there is a difference, why does chrysoberyl have the w