Researchers from GIA’s New York laboratory, Kyaw Soe Moe, Paul Johnson, and Ulrika D’Haenens-Johansson have presented a lab note on the largest blue synthetic diamond. In January 2016, GIA’s New York laboratory examined a 5.03 ct fancy-color HPHT-grown type IIb synthetic diamond produced by NDT, the largest faceted blue laboratory-grown diamond studied so far. Large colorless and near-colorless HPHT-grown diamonds by the Russian company NDT have been investigated, with sizes up to 5.11 carat.

The largest faceted colorless HPHT-grown synthetic diamond reported to date is a 10.02 ct E-color, VS1-clarity specimen, reported by IGI Hong Kong in 2015.

The diamond investigated by GIA, is an emerald-cut synthetic diamond, color graded as Fancy Deep blue, a very attractive color with no other color component, a prized rarity among natural type IIb diamonds.

When viewed under a microscope, faint but sharp color zoning could be seen, indicative of the uneven impurity incorporation of HPHT synthetic diamonds. The diamond has VS1 clarity, only very small metallic inclusions and a cavity observed at the girdle. Fluorescence and phosphorescence images collected using a DiamondView instrument revealed the sample’s cuboctahedral growth pattern, another feature of HPHT synthetics.

This 5.03 carat sample is the largest HPHT-grown blue synthetic diamond examined at a GIA laboratory. As the size and quality of synthetic diamonds improve, careful identification is essential. Representative HPHT synthetic diamond characteristics seen in this specimen, such as the lack of tatami strain patterns (which are typically observed in natural type IIb diamonds), faint but sharp color zoning, and small metallic inclusions from the metal-catalyst flux, can be detected using a gemological microscope, emphasizing its continued importance in gem identification. GIA noted that this is a development that will eventually impact the jewelry industry.