A 3.09 ct CVD lab-grown diamond was recently examined at HRD Antwerp. It is the first time that a CVD synthetic diamond of this size is encountered at the lab. CVD (Chemical Vapour Deposition) is a technique where diamonds are grown in a specially developed growing chamber using a carbon rich gas. Due to chemical reactions, the diamond is formed layer by layer on top of a diamond substrate. This layered growth will result in a rough diamond that looks like a plate. Colourless CVD lab-grown diamonds are grown without the presence of nitrogen. The resulting diamond will therefore always be a type IIa or type IIb diamond (no nitrogen detectable with infrared spectroscopy).
The CVD lab-grown diamond encountered at the HRD Antwerp diamondlab has a brilliant cut (measurements: 9.36 – 9.42 mm x 5.76 mm), a colour grade Slightly Tinted White (I ecg) and fluorescence nil. Microscopic examination revealed the presence of several pinpoint inclusions resulting in the clarity grade VS2. Analysis of the stone with crossed polarization indicated a pattern which is rather similar to the tatami pattern that is characteristic of natural type IIa diamonds.
Both D-screen and Alpha Diamond Analyzer, two screening instruments developed by HRD Antwerp to distinguish possible lab-grown or HPHT treated diamonds from natural diamonds, indicated that the stone needed further testing. Alpha Diamond Analyzer confirmed that the stone is a type IIa diamond and therefore potentially lab-grown or HPHT treated.
Photo : Courtesy of HRD