A diamond expert task force has identified a new type of synthetic blue diamond.
Grown using the chemical vapour deposition (CVD) process, the diamond is said to be inert to short- and long-wave ultraviolet illumination and reveals no specific phosphorescence characteristic of high pressure, high temperature- (HPHT)-grown or natural blue diamonds.
GemResearch Swisslab (GRS) and CGL-GRS Laboratories—led by Jewellery Business gemmology columnist, Branko Deljanin—made the discovery after synthetic blues from .25 carats to more than 1.25 carats were found at both the Bangkok and Hong Kong Gems & Jewellery Fairs in September. Pink, yellow, and colourless varieties of other synthetic diamonds were also found.
The blue lab-grown diamonds are produced with high clarity (VVS2-VS2) and cannot be distinguished from their natural counterparts with a loupe or a microscope. Optical spectroscopy (UV-VIS, FTIR and PL) reveals them to be Type IIa. Their colour is the result of strong absorption of a very intense silicon-related centre. By contrast, both natural and HPHT-grown blue diamond colour is the result of boron impurity.
The silicon-doped blue CVD diamonds are not electrically conductive either.
The labs say the diamonds are being produced by Orion PDC Diamonds, and allege the company does not make a clear enough distinction in its promotional material. In it, Orion refers to lab-grown diamonds as “real diamonds” due to their physical and chemical similarities to natural stones.
A detailed report of the labs’ findings appears in the November 2013 edition of GRS Contribution to Gemmology.
Next to pinks, natural blue diamonds are some of the costliest and rarest diamonds in the world.