GIA Examines 5- and 10-Carat Lab-Grown Diamonds

Carlsbad, Calif.--The Gemological Institute of America recently examined two large lab-grown diamonds submitted to its Hong Kong lab, one of which represents a “significant milestone” in diamond growing.

In a research article authored by Billie “Pui Lai” Law and Wuyi Wang, the GIA said it recently examined a 5.19-carat diamond grown using the chemical vapor deposition process.

The stone, which is J-equivalent color and VS2-equivalent clarity, is the largest CVD-grown diamond examined by the lab to date, and the largest ever reported in the jewelry industry.

Breaking the 5-carat barrier is a “significant milestone” for CVD technology, which has been producing bigger diamonds in recent years, a trend that’s expected to continue.

As the GIA noted, “As diamond growth techniques continue to advance, we expect to see more high-quality samples, both in size and clarity.”

The article also stated that the 5.19-carat diamond was submitted to the lab without proper disclosure.

However, the GIA was able to identify it as a CVD synthetic using its standard screening and testing processes, though the lab noted that black inclusions, which often are contained in synthetic diamonds, were not found in this CVD diamond, meaning it could have been mistaken as a mined diamond if only microscopic examination was used.

The identification of this lab-grown diamond “highlights the importance of using advanced spectroscopic instruments as well as conventional gemological techniques to ensure an accurate identification,” the GIA said.

This 10.08-carat diamond, which has a color grade equivalent to fancy deep blue, was grown using the high-pressure, high-temperature (HPHT) process. (Photo credit: Johnny Leung, courtesy of GIA)
The second article, authored by Wang and Terry “Ping Yu” Poon, discussed the examination of a 10.08-carat blue diamond grown by St. Petersburg, Russia-based New Diamond Technology. NDT is the same company that grew the 5.03-carat blue diamond examined by the GIA’s New York laboratory earlier this year.

Grown using the high-pressure, high-temperature method and disclosed as a synthetic diamond by NDT, the stone is the largest HPHT-grown diamond recorded to date.

The GIA said the emerald-cut stone has a color grade equivalent to fancy deep blue.