Undisclosed Green Synthetics Raise GIA Eyebrows

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)