Fall 2008

Editorial: A New Gemological Challenge: Synthetic Diamond Melee

Alice S. Keller

More than two decades ago, G&G published an editorial by then editor-in-chief Richard T. Liddicoat titled "The Ultimate Synthetic: A Jewelry-Quality Diamond," in the same issue (Winter 1986) that we published an article on the first commercially available gem-quality synthetic diamonds, manufactured by Sumitomo Electric Industries of Japan. Since then, thousands of carats of jewelry-quality synthetic diamonds have gradually entered the marketplace, though the quantities are still very small compared to the millions of carats of natural diamonds produced annually. Most gem-quality synthetic diamonds are grown through high-pressure, high-temperature (HPHT) processes, with the chemical vapor deposition (CVD) method just beginning to establish a presence.

While researchers have succeeded in developing identification methods for both HPHT and CVD synthetic diamonds, melee-size stones (those that weigh 0.20 ct or less) can be particularly troublesome. And the challenges are even greater when dealing with jewelry-set melee. Typically, sophisticated instrumentation is needed to identify even small synthetic goods, and at a certain size it is no longer cost-effective to test each specimen. As a result, most are never submitted to gemological laboratories for identification or grading and are thus sold without a report. Because these goods often have no obvious synthetic characteristics, they can be easily mixed in with a parcel of natural diamonds and sold as such, undisclosed, either to the jewelry manufacturer or—once set—to the consumer.

This is happening, and it’s happening now. That’s what makes the lead article in this issue—Hiroshi Kitawaki et al.’s "Identification of Melee-Size Synthetic Yellow Diamonds in Jewelry"—so important. The study, conducted by three researchers at the GAAJ-Zenhokyo Laboratory in Tokyo, found that 10% of loose yellow melee-size diamonds submitted to the lab over a four-month period were synthetic. Moreover, approximately half the jewelry items set with yellow melee that the lab received during the same period also contained synthetic diamonds. Although there have been many rumors of synthetic diamond melee in the trade over the last several years, this is one of the first research reports to confirm the potential extent of the problem.

To address this issue, the GAAJ-Zenhokyo Lab devised a procedure that combines standard gemological testing with micro-infrared spectroscopy and advanced imaging techniques to distinguish between natural and synthetic diamond melee as small as 0.001 ct. The identification is "fairly rapid," according to the authors, requiring only a few minutes for loose melee and slightly longer for mounted goods.

As the authors point out, synthetic diamonds have by no means saturated the gem market. We feel, though, that the issue comes down to a matter of perception and consumer confidence: Just one undisclosed synthetic diamond out of a hundred casts doubt on the entire parcel—or suite of jewelry. In the group tested by Kitawaki et al., as many as 10 out of a hundred loose yellow melee were synthetic, as was at least one stone in 15 out of 30 melee-set pendants and rings.

Similar problems surround treated melee-size natural diamonds, particularly those that have been HPHT color enhanced or fracture filled (or both). Nor are colored stones exempt, given the challenges posed, for example, by beryllium-diffused corundum in very small sizes. Gems & Gemology applauds the GAAJ-Zenhokyo Laboratory’s groundbreaking work on the cost-effective identification of mounted synthetic diamond melee. At the same time, we also call on gemologists and research facilities everywhere to continue to develop realistic means to confront such identification challenges for small and lower-cost stones, for the sake of the consumer and the industry.

The words with which Richard Liddicoat concluded his 1986 editorial continue to resonate today: " . . . never has the role of the gemologist been more important."

Alice S. Keller
Editor-in-Chief