While in Carlsbad, Calif. for Gemological Institute of America’s (GIA) Symposium last month, the never-shy Martin Rapaport twice publicly named one specific high-end jeweler for selling what could be high-pressure, high-temperature-treated (HPHT) yellow melee in their stores.

As a reporter, my ears perk up when I hear comments such as these. Does Rapaport, an industry veteran, have the inside scoop on jewelry’s next big scandal? Does he know about a big, complicated lawsuit that involves pouring over hundreds pages of dense court documents until you go cross-eyed?

As it turns out, no. Rapaport later said he had no evidence that this particular jeweler was selling HPHT-treated yellow melee. He was simply calling to light an issue that has arisen in the industry and could impact any jeweler: HPHT-treated yellow melee.

HPHT-treated yellow melee (pictured below) is more difficult to identify as being treated than irradiated yellow melee, said Tom Moses, GIA’s senior vice president of laboratory and research. The instrumentation needed to detect HPHT-treated yellow melee is a bit more sophisticated and, visually, they do not stand out as being treated.


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Yellow melee treated with irradiation takes on more of a “taxi-cab yellow” tone (a comparison I can appreciate fully living in New York City) while the HPHT-treated yellow melee “blends in more,” Moses said. He added that yellow HPHT-treated melee also more closely resembles its natural counterparts than HPHT-treated blue or pink melee, which tends to look unnaturally bright.

“There’s no question it can create a big challenge,” he said. “The colors produced with that kind of treatment overlap pretty well with colors that occur naturally. An unsuspecting person that deals in this kind of thing could, in fact, be fooled.”

As many of you already know, HPHT has been around for a number of years but, in industry-treatment terms, is a relatively new process. The trend toward using the treatment on smaller stones is on that has increased in recent years as the process has evolved, spreading first to natural colored diamonds and then to smaller and smaller diamonds.

“Not every large stone is an acceptable candidate for the (HPHT) process,” Moses said. “When you run out of those stones, you look to do other things.”

His advice for the industry: deal with people you trust. Know your suppliers well enough to know that you’re not being sold HPHT-treated goods that aren’t identified as such.

Unless you have 100 percent confidence in your supplier, then submit a random sample of yellow melee to a well-equipped and well-staffed grading lab for testing.

Jewelers should check with their preferred lab to see what kind of, if any, testing services are available for melee and to make sure the lab has the necessary equipment to detect HPHT-treated melee.



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Filed Under: Science
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