Image credit: NGTC
The Beijing Laboratory and Shenzhen Laboratory of National Gemstone Testing Center (NGTC) recently received several yellow laboratory-grown diamonds through the chemical vapour deposition (CVD) method, which were required to be further tested on identification and quality evaluation, says NGTC.
According to NGTC, the results showed the weight of the tested yellow CVD-grown diamonds as about 1-2ct, with the largest one of 1.81ct. The colour of the CVD-grown diamonds varied from pale yellow to dark brownish yellow, including pure bright yellow.
Also, NGTC said there were some typical inclusions in these CVD-grown diamonds, including pinpoint dark-colour inclusions or dark-colour inclusions distributed layer by layer. Through testing, the yellow CVD diamond is type Ib with the main components of isolated nitrogen atoms. After being produced in the lab, these diamonds are processed in high temperature and high-pressure conditions to get rid of the brownness hue and enhance the transparency of diamonds.
NGTC says that it has conducted systematic tests and research on the new variety of CVD synthetic diamond, and the related research will be published in academic journals soon.
The diamond research team of NGTC said that at present, NGTC Laboratories can precisely distinguish the natural, laboratory-grown, and treated diamonds.
On December 30, 2020, NGTC published the Enterprises Standard of identification and quality evaluation of laboratory-grown diamond (Q/NGTC-J-SZ-0001—2020), which took into effect from February 1 2021. NGTC Laboratories could issue identification and quality evaluation certificates for all.
Aruna Gaitonde, Editor in Chief of the Asian Bureau, Rough&Polished
