AGTA GTC Laboratory Update
Welcome to AGTA GTC's Laboratory Update for August 22, 2007
In this message- Special Offer on Origin Reports
- International Gemological Conference in Moscow
- Surface Coating of Topaz
Current turnaround time at the AGTA GTC 5–8 Business Days |
Special 2-for-1 Offer on Origin Reports
The American Gem Trade Association Gemological Testing Center is offering our clients a special offer from August 27 to September 7, 2007. Any ruby, sapphire or emerald submitted for an Origin Report during that period will be given a free ID Report for a gem of the same size or smaller submitted at the same time. Yes, you heard right, one paid Origin Report earns a free ID Report on a second gem.
This offer will be valid from Monday, August 27 through Friday, September 7, 2007. Start getting your gems ready now!
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International Gemological Conference in Russia
By Dr. Lore Kiefert, AGTA GTC
Wow! 200 scientists and gemstone experts under one roof. And among them some of the most famous names like J. Shigley, J. Koivula, D. Schwarz, K. Schmetzer, R. Kane, H.A. Hänni, V. Balitsky, Tay T. Sun, M. Ou Yang, W. Atichat, P. Wathanakul, A. Abduriym, I. Sunagawa, G. Zoysa, E. Fritsch, G. Bosshart, S. McClure, E. Strack, and and and…
This promised a full four days of concentrated knowledge. And that's what it was: lectures starting at 9 AM, lunch in the canteen of the Academy, back to lectures, out after 6 PM. The lectures covered all fields of gemology and gem deposits, from the Russian diamond mines in Archangelsk, Yakutia and Siberia to colored gemstone deposits in Russia, Sri Lanka, Thailand, Madagascar and many other places. Overviews of synthetic gemstones, the distinction between them and their natural counterparts, lots about the detection of diamond treatments, Be-treated corundum, and many other rare and common gemstones. Also included were lectures about pearls and pearl farming, an overview on the origin of historic gemstones, and lectures about fashioning and marketing all these products.
But this wasn't enough. One afternoon was spent in the Diamond Fund of the Kremlin. This impressive visit showed major quantities of large diamond octahedrons, large faceted diamonds, huge gold nuggets and fashioned jewelry, as well as fashion and lifestyle in the czar era. "Diamond World," a diamond cutting and fashioning center, as well as the Fersman Mineralogical Museum with an excellent collection of mineral specimen all over Russia and elsewhere, were also visited.
Packed with so much information, you would think the conference would have been enough. But no, the best part was yet to come – the trip to the Malysheva emerald mine and the demantoid mines, both near Yekaterinburg. The readers of our newsflash may remember that Richard Hughes visited Malysheva the year before. However, if such a trip is organized in connection with a conference from a local professor, the mine owners make concessions they would not do otherwise. During the three days in Yekaterinburg, we could take photos of whatever we wanted, in the mines as well as in the museums we visited. This was a great honor, because usually photos are not allowed. This way we could take photos in the emerald mine as well as in the sorting plant and we were shown their latest production. Below are some impressions of this trip.
The group standing at the line that separates Europe from Asia, just outside of Yekaterinburg. |
A large emerald crystal on display in the sorting room at Malysheva. Photo: Lore Kiefert |
In the tunnels at Russia's Malysheva emerald mines. Photo: Lore Kiefert |
Looking for emeralds and alexandrites on the ore belts at Russia's Malysheva emerald mines. Photo: Lore Kiefert |
Surface Coating of Topaz
Various types of surface treated topaz have become increasingly popular in the gem market, and the coatings can be found in all colors. Mostly the coatings are easily scratched off. These coatings are either produced by a thin coating of a metal, metal oxide, nitride, sulfide or carbon. Another method to obtain thin layers is an optical interference coating of alternating layers of materials with relatively high refractive indices and relatively low refractive indices. A third method is the coating of transparent ink including a red, blue, green, or yellow dye [1].
Some of the resulting colors, especially the pink ones, prove to be deceiving to the gemologist at first because the coating is generally on the pavilion – not on the table of the stones. So when analyzed by EDXRF, which is normally done on the table, only the usual topaz composition is detected, but no special elements. Only when turned on its side, the high concentration of an element can be detected. The authors tested 22 of these types of coated topaz with different hues.
Different flavors of coated topaz. |
For a more permanent surface coating, two major techniques are used. The first technique is based on heat treatment of faceted gem materials in a transition metal-bearing powder. The second major technique requires two steps of treatment:
- The deposition of a coating on the faceted gemstone and
- Heat treatment of the coated gemstone [1]
There is some controversy if topaz treated via these methods is coated or diffused. We have analyzed some of these samples and found out that indeed the coloring agent does not come off as easily as in the usual coated topaz. We tried scratching and leaving the samples in acetone without affecting the coating. Subsequent electron microprobe analysis on the interface of the topaz and the colored layers did not show any signs of diffusion of the coloring agent into the material. However, in light of recent developments concerning irradiated topaz and the difficulties for many gem dealers to obtain licenses for this type of material, the coatings on the Swarovski (Signity) and Leslie topaz may be a very attractive alternative.
Reference
- [1] Schmetzer, K. (2006): Surface coating of gemstones, especially topaz – a review of recent patent literature. Journal of Gemmology, Vol. 30, No. 1/2, pp. 83–90.
The AGTA Gemological Testing Center provides the industry and the public with a complete range of lab services including gemstone identification, origin determination and pearl identification. Located in New York City, the laboratory is equipped with the latest, technologically advanced, investigative equipment. The AGTA GTC is committed to providing excellent service and superior value. A complete list of services and pricing information is at www.agta-gtc.org. Please contact us with any questions.
