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Press Release: The New York-based gemological lab Analytical Gemology & Jewelry (AG&J) warned the trade of new, harder-to-detect chemical vapor deposition (CVD) diamonds being sold as natural, type IIa brown stones. A batch of these stones was recently submitted by a client as natural high pressure-high temperature (HPHT)-treated diamonds and contained 75 percent CVD-grown HPHT-treated diamonds. The stones were purchased from a trade source with which the client had a long-standing business relationship. The AG&J laboratory specializes in the identification of diamonds and their treatments. They are reporting a new alarming find with permission from their client, a U.S. gem dealer specializing in HPHT-treated diamonds with more than a decade of experience. AG&J determined that a batch consisting of 18 (17 round and one marquise-cut) diamonds weighing a total of 6 carats, ranging in size from 0.14-carat to 0.635mm, color ranging from F to gray and a clarity range from VVS to SI, was submitted to the lab at the end of July 2013. Identification was done with their proprietary diamond testing system, which can also be used to test melee diamonds, as previously reported. AG&J identified 13 CVD grown HPHT treated synthetic diamonds.  The stones were purchased on the open market in Mumbai as type IIa brown diamonds. The buyer used a portable FTIR instrument to test the stones during the purchase and to make sure he only buys diamonds that are type IIa or very low nitrogen type Ia stones intended for HPHT treatment. The HPHT treatment was done at a facility by means of a cubic press, using undisclosed parameters. AG&J were, nevertheless, able to conclude from their tests that the HPHT facility tried to enhance the color by using a range of different time and temperature parameters. The client grew suspicious after the HPHT treatment did not give the expected results. Several stones from the parcel turned into a gray color, while the highest color was only I. After submission to AG&J, it turned out that 13 of the 18 stones were CVD grown HPHT treated synthetic diamonds. It also turned out that the CVD stones were produced using different parameters and reactors, which supports the conclusion that they came from different factories, indicating that the number of facilities for CVD diamonds is growing rapidly. According to AG&J’s experience, their research database but also reports from other researchers, all 13 diamonds are not coming out of the Gemesis production line. “It was not surprising that the client could not detect the CVD diamonds using FTIR spectroscopy,” said AG&J's CEO, Dusan Simic, “as this requires more sophisticated methods that also have to keep up with changes in the production of CVD and HPHT-grown stones as well as all treatments.” Responding to the trade’s concern of rapidly growing occurrences of synthetic and treated diamonds mixed in natural batches, and in mounted jewelry, AG&J developed a system for batch testing diamonds accurately in a cost-effective way. The system is based on internationally accepted diamond identification methods, such as: Raman spectroscopy, absorbance measurement in the UV-VIS-NIR range, and FTIR and Photoluminescence. Simic said, “These recent findings tell us that the production of CVD diamonds became so cheap that they start to penetrate the low-cost market. It is just a matter of time until commercially available HPHT treatments will be improved in a way that low-quality CVD stones can be turned into diamonds of highest color.” For more information, contact Simic directly at dusan-at-agandj.com; visit the lab online at www.agandj.com. About AG&J
Analytical Gemology and Jewelry is a gemological laboratory located in New York’s Diamond District, specializing in the identification of diamonds and their treatments. The laboratory is equipped with state-of-the-art equipment, including a Renishaw Raman with multiple lasers, and applies proprietary procedures for sophisticated gemological analysis. For more information, visit their website at www.agandj.com.
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