The ABCs of HPHT

The ABCs of HPHT

JCK Magazine –– Twelve years ago this summer, the HPHT (high pressure/high temperature) process was introduced to the diamond industry, sparking what GIA then-president William E. Boyajian called “the biggest gemological crisis” in his 23 years at the Institute. At the 1999 GIA Symposium, an uproar erupted over the then-­undetectable treatment and its potential to capsize consumer confidence.

Since then, the diamond industry has coped with far more serious crises, and HPHT has remained mostly a nonissue. And while it’s no longer considered undetectable and has yet to generate any negative publicity for the industry, HPHT is still viewed warily by a good portion of the trade. GIA recently shocked the industry by announcing it has seen bigger—often undisclosed—HPHT stones at its grading lab. Meanwhile, the people behind the process complain they’re the victims of unfair, for lack of a better word: treatment. David Bennett, president of Worthington, Ohio–based HPHT producer Bellataire, says his biggest problem is “fighting negativity from people who really don’t understand what the product is.”

So what exactly is the product? The irreversible, permanent treatment, sometimes called “annealing,” subjects brown type IIa stones, which have minute amounts of nitrogen, to enormous amounts of pressure and heat — as high as 2,600 degrees Celsius—to replicate the forces that produce diamonds in nature. After 15 minutes, a stone’s color grade can jump dramatically. If it contains a bit of nitrogen, it can turn yellow or green, or, with the right irradiation, pink. Currently, only two companies openly perform the process in the United States.

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