Updates on the research work of the Gemological Institute of America’s Gem Trade Laboratory was provided in a fascinating Wednesday session featuring Dr. James Shigley, GIA director of research, and Shane McClure, director of GIA GTL’s West Coast Gem Identification services.
One hot topic dealt with HPHT treatment (“high pressure, high temperature”) of diamonds, which turns some varieties of brown diamonds white. The process was perfected four years ago by General Electric.
Identifying HTPT diamonds has been “a challenge” for several years, said Shigley, and, logistically, the problem is growing as more HTPT-treated diamonds enter the market. In the beginning, most of the HPHT-treated diamonds that GIA GTL saw were Type II, but more Type 1 diamonds—the most common type—are coming onto the market, from labs and large companies here as well as from overseas companies, especially ones from Russia and China. “And they don’t always come with a label saying they’ve been treated,” Shigley noted.
However, GIA has made “great progress” in dealing with HPHT—which its originators once claimed was undetectable—by focusing on three areas:
· Identifying organizations here and elsewhere that are doing the treatment, and getting their cooperation on what they do and what they treat.
· Documenting the various forms of treatment. GIA now has a database of “thousands of known and unknown HPHT treated diamonds.”
· Doing its own experiments to develop the treatment and testing possible identification criteria. “We’ve been able to successfully replicate many of the treatments we’re seeing in the trade,” said Shigley. Some of those visual identification features GIA research has already found include “the graphization of inclusions, damaged solid inclusions, and heat damaged surfaces.”