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Undisclosed Green Synthetics Raise GIA Eyebrows

Carlsbad lab receives 25 HPHT stones with unusual color.
May 26, 2019 11:11 AM   By Rapaport News
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RAPAPORT... Twenty-five undisclosed lab-grown diamonds have turned up at the Gemological Institute of America (GIA) — including several with a rare greenish color.

The GIA’s lab in Carlsbad, California, recently received the stones — weighing from 0.46 to 0.52 carats — for grading reports. They all proved to have been created using High Pressure-High Temperature (HPHT), GIA senior research scientist Sally Eaton-Magaña explained in a lab note published in the Spring 2019 issue of Gems & Gemology, the institute’s quarterly scientific journal.

While nine of the stones were colorless or near-colorless, eight had faint-yellow-green color, seven were faint green, and one was very light green. The coloring resulted from a high concentration of nickel, an impurity that’s common in HPHT, but rarely in large enough amounts to affect the color, Eaton-Magaña explained. (In diamonds at large, nickel can cause a green hue.) GIA gemologists previously reported on a fancy-deep-yellowish-green HPHT diamond in 2017, with nickel also the cause in that case.

“As laboratory-grown-diamond manufacturers continue to experiment with their recipes and the process further evolves, we will likely see greater quantities and a wider variety of color ranges,” Eaton-Magaña wrote. The occasion also gave a rare opportunity to analyze a large dataset of similar but unusually colored HPHT diamonds, she noted.

The Spring edition of Gems & Gemology also reported on a natural diamond with a synthetic layer — the second such case the GIA had seen in about two years.

Image: A 0.50-carat, faint-green HPHT synthetic diamond. (Robison McMurtry/GIA)
Tags: California, carlsbad, Gemological Institute of America, gems & gemology, GIA, High Pressure-High Temperature, HPHT, lab-grown diamonds, Rapaport News, Sally Eaton-Magaña, Synthetics, undisclosed synthetics
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