A Key to Synthetic Diamond ID?

Most retail jewelers show little interest in synthetic near-colorless diamonds, since widespread commercial availability still looks to be a few years off. Nevertheless, one gemologist has been working to prevent the inevitable retail jeweler’s nightmare: unwittingly buying and selling a synthetic diamond.

“A definitive identification for synthetic near-colorless diamond may be at hand,” says Martin Haske of Adamas Gemological Laboratory in Brookline, Mass. Haske is the developer of the SAS2000, a portable laptop-size spectrophotometer. Using newly developed instrumentation adapted for the SAS2000, Haske has uncovered a fairly reliable diagnostic characteristic spectrum for synthetic near-colorless diamond.

This latest version of the desktop instrument includes UV/VIS spectroscopy as well as a $10,000 Raman/photoluminescence spectroscope add-on, a miniaturized version of the $250,000 desk-sized unit that other laboratories-including GIA and AGTA-are now using. According to Haske, the portable spectrophotometer gives fairly detailed results at room temperature, unlike others that primarily use liquid nitrogen to cool the gemstone to temperatures far below freezing. However, with his souped-up version of the SAS2000, Haske also has developed a container to hold diamonds in liquid nitrogen, just like the professional labs, for users who prefer that method.

To date, Haske has tested 46 synthetic diamonds from more than three years of Russian near-colorless synthetic diamond production; 24 large Chatham near-colorless rough synthetic diamond crystals, also produced in Russia; and nine smaller faceted near-colorless synthetic diamonds of recent Ukraine production supplied by The Morion Company. More than 70% of the stones Haske examined showed a discernible 694nm spectrum peak, with more than 30% showing the peak quite readily. Such results are “unpublished in the literature at this time, to our knowledge-you may be witnessing diamond diagnostic history,” claims Haske.

GIA, however, was unimpressed with the discovery and not convinced of the importance of Haske’s findings. “We are examining colorless and near-colorless natural and synthetic diamonds to see whether this criterion (referred to in the inquiry) is valid,” notes GIA public relations officer Alex Angelle. Although two different studies of synthetic diamonds have been reported in GIA’s Gems & Gemology, Haske says that neither made reference to the spectra that he believes hold the key to making the identification.

Haske doesn’t understand why GIA feels it’s necessary to examine more synthetic diamonds. “GIA has seen most, if not all, of Tom Chatham’s synthetic diamond produced in Russia,” says Haske. “I’ve seen the feature on 27 out of 33 samples. Maybe they only tested a very limited sample, or maybe they need an SAS2000.”

“Colorless synthetic diamonds can be identified using standard gemological techniques,” claims Angelle. He cites articles describing the gemological properties of synthetic diamonds: J.E. Shigley, E. Fritsch, I. Reinitz, T.M. Moses: “A Chart for the Separation of Natural and Synthetic Diamonds,” Gems & Gemology, Winter 1995; and C.M. Welbourn, M. Cooper, P.M. Spear, “De Beers Natural versus Synthetic Diamond Verification Instruments,” Gems & Gemology, Fall 1996.

But synthetic manufacturers now claim to be perfecting the synthetic growth process, leaving few if any inclusion or graining clues that the laboratory gemologist can discern. Computerized spectrophotometry soon may be the only way to identify these gems. Haske, undaunted by GIA’s snub, reports that “there appears to be a correlation between the existence of short-wave UV fluorescence or phosphorescence and the existence of the 694nm peak found in these synthetic near-colorless diamonds.” It has been suggested that the high level of impurities may quench any short-wave fluorescence or phosphorescence. Fluorescence or phosphorescence then may not exist in near-colorless synthetic diamonds, and the 694nm peak may be the only identifying feature.