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NGTC laboratory discloses new variety of “pure bright yellow” CVD-grown diamonds


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 are different from the previous grown method.

These yellow CVD-grown diamonds received by the laboratory weighed between 1-2ct, with the largest one of 1.81ct. The color of the CVD-grown diamonds varied from pale yellow to dark brownish yellow, including pure bright yellow. 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.

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