GIA Spots CVD Stone in Parcel of Treated Melee

RAPAPORT... In a rare case, the Gemological Institute of America (GIA)has discovered a color-treated lab-grown diamond in a batch of natural melee aclient had submitted for testing. The GIA's Tokyo laboratory found the 0.007-carat, irradiatedgreen-blue chemical vapor deposition (CVD) diamond in a parcel of 300 similarlycolored irradiated stones, it said in a recent journal article. The other 299diamonds were natural, but had too been exposed to an artificial source ofradiation to improve their color. All 300 stones were round, with the parcelweighing a total of 1.97 carats. "Irradiated CVD synthetic diamonds are rarely seen at GIA,which had examined only six of them before this report," Shoko Odake, aresearch scientist at the GIA in Tokyo, wrote in the Winter 2018 edition of theinstitute's quarterly journal, Gems & Gemology. "Previously reportedirradiated CVD synthetic diamonds were relatively large, from 0.43 to 1.34carats. This is the first melee-sized irradiated CVD synthetic diamond examinedby GIA." The GIA often identifies synthetic melee mixed in withnatural diamonds, though most cases involve colorless stones. In the Winter2014 issue of Gems & Gemology, researchers in New York revealed theyhad found 14 High Pressure-High Temperature (HPHT) synthetics and oneHPHT-treated natural diamond in a parcel of 359 yellow melee diamonds. Image: The 300 green-blue diamonds the GIA screened, with the CVD stone on the far right. (Shunsuke Nagai/GIA)