THE LARGEST UNDISCLOSED SYNTHETIC DIAMOND EVER IDENTIFIED BY GIA

A 5.19ct cushion modified brillant synthetic diamond has been identified by the GIA in Hong Kong. It was not disclosed as a synthetic.

It is a high quality stone of J colour and VS2 clarity. It did not contain any black inclusions which are typically a strong sign of synthetics.

After the examination, the stone was laser inscribed with the words “Laboratory Grown” on the girdle.

Needles and pinpoints were the major internal features. Black inclusions, a common feature of CVD synthetic diamond, were not observed. Photo by Billie “Pui Lai” Law. — Needles and pinpoints were the major internal features. Black inclusions, a common feature of CVD synthetic diamond, were not observed.

The detailed story of how the GIA deduced that this diamond was not genuine is quite interesting. Read more here:
http://www.gia.edu/gems-gemology/winter-2016-labnotes-CVD-synthetic-diamond-over-5-carats-identified