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Colored Gemstone

Diamond Treatments Re-examined

Diamond issues played an important role at this year’s World of Gems Conference.

By Gary Roskin
More than 150 gemologists and appraisers attended the World of Gems Conference (WOGC) produced by Gemworld International in Chicago in October. Focusing on diamond presentations, day one included an update and sobering view of diamond treatments from Dr. James Shigley, research fellow at the Gemological Institute of America (GIA).

Clarity enhancements haven’t changed much over the past several decades and identification still appears to be fairly easy, even for the desk gemologist and diamond grader. But color enhancements have become so scientifically complex, they require more sophisticated scientific instrumentation, such as infrared spectroscopy with liquid nitrogen, leaving the desk gemologist and diamond grader to rely heavily on professional gem laboratories.

With the advent of High Pressure-High Temperature (HPHT) processing, along with additional steps of irradiation and annealing, or heating, determination of color origin is becoming quite the challenge. Shigley spoke of “diamond types” and possible color effects from the combinations of HPHT and irradiation, but stopped short of giving out full details. “People use that information to get around our identification methods,” he explained. So, while GIA would like to present gemological identification features used to determine whether the color is natural or enhanced, too much information leads to more difficult identifications in the future. After all, treated diamonds go through processes similar to naturally colored diamonds.

While identification research is moving forward, new multiple-step treatments are moving forward as well. This poses a real challenge for the labs. After all, as Shigley pointed out, “People don’t tell us what they’re doing.” Building a larger database of known natural and treated diamonds is key for the future of treatment identification.

Coating technology is causing some concern in the labs. Serenity Technologies’ new nanocrystalline layer — a super-thin coating of diamond — is so far undetectable by the major gem labs. At this point, there is no noticeable enhancement from this process — no signs of improved durability or of misidentification using a diamond probe — and so the issue of detection seems to be purely academic. But, in time, this technology could be problematic.

International Perspective

Jon Phillips, divisional manager for Canada’s Corona Jewellery Company, discussed an “International Perspective” on diamond issues. Phillips holds positions with several diamond industry organizations, including the standards committee of the Responsible Jewellery Council (RJC). He is vice president of the CIBJO Diamond Commission, as well as a member of the World Federation of Diamond Bourses (WFDB). Focused on responsible practices, fair trade and the Kimberley Process (KP), Phillips spoke about how difficult it is to establish priorities and directions. “You mine diamonds in Africa, and they go to Antwerp where they are sold to be cut in China, or India. They then end up in Chicago, or Hong Kong. They’ve gone 20,000 miles, through five or more companies.... Just how are we supposed to keep track of these diamonds?” Through industry ethics, advises Phillips, as well as by working within organizations such as RJC, International Diamond Council (IDC), World Diamond Council (WDC), CIBJO, International Diamond Manufacturers Association (IDMA) and the WFDB. Phillips pointed to the many actions these organizations have taken to improve the ethics of trading diamonds. Of course, the KP has been under fire the past several months, and news of an expanded KP program is a possible solution. Phillips told the audience to “watch for it.”

Fluorescence

Color grading fluorescent diamonds has been a hot topic for the past several years, and yet another panel discussion on the merits of grading using non-ultraviolet (UV) lighting was presented at the conference. On the panel were Lalit Aggarwal, with ImaGem; Richard Drucker, president of Gemworld International; Joe DuMouchelle of DuMouchelle Auction House; Diane Flora, education director at the American Gem Society (AGS); Antoinette Matlins, author and Tom Tashey, with Professional Gem Sciences and Phillips.

It was argued that color grading using non-UV lighting gives a more true body color grade, but no consensus seemed apparent as to whether or not this type of grading would be accepted in the trade. The GIA and other grading laboratories use lighting that does have UV content but they are grading at a distance where the UV has limited effect.

DuMouchelle noted that prior to 2008, fluorescence was not much of an issue. Since 2008, however, dealers have noted that if the diamond had any noticeable fluorescence — medium or stronger — they were not interested. From the consumer viewpoint, however, if it is not a clarity characteristic, they do not care if the diamond shows fluorescence or not. Matlins seemed to feel that since the consumer notices a color difference from one lighting environment to another with strongly fluorescent diamonds, the industry should consider changing the grading environment. “The way diamonds are graded today in the lab, it’s a misrepresentation of the actual color grade,” says Matlins. “UV is still impacting the color, even in the diamond doc. The color I am going to see 90 percent of the time is not worth the 10 percent discount … it should be more!” And the debate rages on.

Wrapping up diamond issues at the conference, Shigley discussed the emerging synthetic diamond industry. Again pointing to a stronger database, Shigley noted that GIA was focused on recording data on known synthetic properties, making it easier to separate the natural from the lab-grown materials. HPHT-grown diamonds are fairly common and are relatively easy to identify.

But it is the Carbon Vapor Deposition (CVD) diamond from Apollo Diamonds that could eventually be of greater concern. So far, however, Shigley feels confident that the laboratories can identify all CVD-grown diamonds entering the lab. After news broke of larger CVD diamond crystals grown by the Carnegie Institute, the gem industry was very concerned. But, as Shigley pointed out, there are much more valuable applications for large CVD diamond crystals, including windows in space travel, as well as in computer chip technology. Shigley advised the audience that, in the future, they should be more alert to possible CVD coatings on other gem materials.

 

Article from the Rapaport Magazine - November 2010. To subscribe click here.

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