agta-agl release
TRANSCRIPT
-
8/14/2019 AGTA-AGL release
1/2
FOR IMMEDIATE RELEASE
AGTA-GTC and AGL IDENTIFY NEW TANZANITE TREATMENT.
NEW YORK, NY 23 May 2008Recently the American Gem Trade Association Gemological TestingCenter (AGTA-GTC) and American Gemological Laboratories (AGL) received a number of facetedtanzanite samples that were determined to have been coated. Evan Caplan of Omi Gems, Inc. sentsamples to several labs after a light repolishing of a few stones resulted in a noticeable loss of color.
Until now, we had not identified a coating on tanzanite to improve its color. indicated Dr. Lore Kiefert,Director of the AGTA-GTC.
Although the coating is not immediately obvious, careful examination with a microscope and inimmersion provided clear indications of the coating in most instances. stated Christopher P. Smith, VicePresident and Chief Gemologist of AGL This was evidenced by abrasions along facet junctions and atthe culet where the coating had worn off, as well as a subtle iridescence when viewing the surface with
reflected light. Smith further added.
Advanced analytical testing identified that the coating contained cobalt. The most reliable means tosubstantiate the presence of the coating is the use of X-ray fluorescence spectroscopy. Kiefert explainedThe coating is colored by cobalt, which is readily detected using this analytical technique.
Although the gemstone industry has become very familiar with the practice of heating zoisite to achievethe best violet to blue color in tanzanite, these stones represent the first time either lab has identified acolor-enhancing coating on tanzanite.
The majority of the tanzanite sample was comprised of smaller calibrated stones. Fine color tanzanite inthis size range is rarely sent to a lab and therefore would avoid detection unless closely scrutinized. Thisis just another reminder that each and every gemstone should be fully examined to determine whether or
not it has been treated. Smith indicated Today, it is not uncommon to see stones that have been treatedusing multiple or compound techniques to achieve a particular result.
As a closing statement, both Kiefert and Smith emphasized Any treatment used to modify the color of agem should be disclosed. Coatings in particular are not considered permanent and in the U.S. arerequired by FTC guidelines to be properly disclosed at the point of sale.
Figure 1: These two tanzanites were part of agroup of stones recently examined at both theAGTA-GTC and AGL facilities in New York.
Both were identified as having a thin coatinglayer to artificially improve their color.Photograph by Fred Kahn and Sun Joo Chung.
-
8/14/2019 AGTA-AGL release
2/2
# # #
About American Gem Trade Association-Gem Testing CenterThe American Gem Trade Association is a not-for-profit Association serving the natural colored gemstoneand cultured pearl industry since 1981. The AGTA serves the industry as "The Authority in Color" and hasits headquarter office in Dallas, Texas and the world-renowned Gemological Testing Center in New York,New York (www.agta-gtc.org).
About American Gemological LaboratoriesFounded in 1977 by C. R. Cap Beesley, American Gemological Laboratories (AGL), a subsidiary of thepublicly traded Collectors Universe (NASDAQ: CLCT), pioneered the development of the worlds firstcomprehensive Colored Stone Grading System (www.aglgemlab.com) AGL has also provided detailedcountry of origin and enhancement reports for some of the most prestigious retailers and auction housesin the world for the past three decades. In 2007, AGL was the designated official North Americanlaboratory of the International Colored Gemstone Association (ICA). In addition, the laboratory is the
official colored gemstone laboratory of the 2007 Fine Jewelry CEO Summit and the JCK Las VegasShows, as well as the 2007 Platinum Sponsor of the ICA World Congress in Dubai.
Contacts:
Dr. Lore Kiefert Christopher P. SmithDirector Vice President and Chief GemologistAGTA-GTC [email protected] [email protected]
Figure 3: In immersion it was also noted thatalong facet junctions and at the culet the colorwas lighter. This was a result of where thecoating had been abraded away, revealing thelighter, inherent color of the tanzanite.Photomicrograph by Christopher P. Smith
Figure 2: The cobalt-coating produced asubtle iridescence that could be seen whenobserving the stones surface in reflectedlight. The rectangular area near the point ofthis facet also highlights an area on the hosttanzanite where the coating did not adhere.Photomicrograph by Christopher P. Smith
http://www.agta-gtc.org/http://www.aglgemlab.com/mailto:[email protected]:[email protected]:[email protected]:[email protected]://www.aglgemlab.com/http://www.agta-gtc.org/