GemSelect Newsletter - January 2009
In our newsletter this month:
Unheated Sapphire Back to Top
It's a fact of life in the gemstone industry that many gems are enhanced or treated. The most common form of treatment is heat treatment, which is applied routinely to ruby and sapphire, and to other gems such as tanzanite, blue zircon and blue apatite. Some gems, such as blue topaz, are irradiated to produce their distinctive color; in fact it's virtually impossible to buy a blue topaz which has not been irradiated. Other gems, such as emerald, are treated with oil or resin to fill fractures. More recently, we've seen heat treatment with beryllium diffusion for yellow and orange sapphire, and fracture-filling with lead glass for African ruby. Sometimes it seems like the gemstone world is awash in gem treatments.
If you have the impression that these days almost all gems are treated, please think again. Of our current inventory at GemSelect (over 9,000 gems) about 75% are completely untreated. Most types of gemstones are not treated, and that includes a number of gemstone varieties with excellent hardness and brillance, such as spinel, all the types of garnet, tourmaline, peridot and orange, brown and rose zircon.
While the vast majority of sapphires are heat treated, it is still possible to find completely untreated sapphire gems. They are rare and relatively expensive, but we have recently found a new source and have been adding more of them to our stock. Most of the unheated sapphire gems we've been buying are from Tanzania, long a famous source for tanzanite and tsavorite garnet. We have also found some unheated sapphire gems from Madagascar, Australia and Thailand.
We have acquired unheated Tanzanian sapphire in pink, violet and violet-blue, including some stunning color change pieces. Some of the unheated blue sapphires from Madagascar and Australia are found in large sizes (weighing over 2 carats) and display a velvety texture from rutile silk inclusions that you will only find in unheated sapphires, since the rutile tends to melt when sapphire is heat-treated. We've taken a number of our unheated sapphires to gemological labs for testing, and are confident that all are unheated. If you would like a gemological certificate, just check add gem certificate when you purchase your sapphire and we'll obtain a certificate for you.
Rare and Unusual Gems Back to Top
Each month we feature a rare and unusual gem from our inventory. This month we feature an exceptionally large tanzanite from Tanzania.
Natural Tanzanite Gemstones
To date, tanzanite has been found only in one location in Tanzania. Not only is it rare, but also the industry faces the unhappy prospect that eventually the mines will be worked out. The market demand for tanzanite is so great that prices have been driven higher and higher, and even second rate pieces sell at prices comparable to fine sapphire. So finding a really outstanding tanzanite in a large size can be very difficult. This 10.76 carat piece is the finest tanzanite we've had in our inventory. The color is a rich violet-blue and it has a nicely executed cushion cut. Its clarity is excellent and the gem has been graded VVS.
Customer Questions Back to Top
Every month we answer questions of general interest from our customers. Please feel free to send your questions or suggestions to our support team at email@example.com!
How do I determine that a sapphire has not been heated? What do I look for? Your advice is appreciated, MRJ, UK.
Determining conclusively that a sapphire has not been heat-treated is something that only a very experienced gemologist can do. Gemologists examine internal structures under high magnification and look for the presence of crystal structures that would be altered by heat treatment, since many charactertistic inclusions such as rutile and zircon crystals have a lower melting point than corundum. Some laboratories also use high-tech tools such as Raman spectroscopy and laser tomography.
Can you certify country of origin in your gem certificates? KJ, USA.
We currently offer identification reports from independent gemological labs that do not certify country of origin. However, there is growing interest in certifying gemstone origin and a number of labs have done (or are doing) research to enable them to provide country of origin certification. Please be aware that the results are not always conclusive, and most labs offer their identification as a "considered opinion" only. For more information on the issue please see our recent article on country of origin.
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