By Michelle Graff
michelle.graff@nationaljeweler.com
A factory in China is producing a large number of colorless, gem-quality diamonds grown using the high-pressure, high-temperature (HPHT) process. The GIA said these crystals have typical cuboctahedral morphology and weigh up to 3.5 carats. (Photo used with permission of the GIA, credit Jianxin (Jae) Liao.)

Carlsbad, Calif.--The Gemological Institute of America said it expects even more large lab-grown diamonds produced using the high-pressure, high-temperature (HPHT) method to enter the supply pipeline in the future.

In an article slated to appear in the spring 2016 issue of Gems & Gemology and published on GIA.edu now, the GIA’s Tom Moses and Wuyi Wang described their experience at Jinan Zhongwu New Materials Co. Ltd., a diamond-growing factory in Shandong, China. The GIA asked and, subsequently, was granted permission to visit this factory.

There, Moses, the GIA’s chief laboratory and research officer, and Wang, the director of research and development, obtained 50 crystals ranging in size from 0.5 to 1.2 carats. All were readily identifiable as synthetic using the same instrumentation and techniques applied to diamonds submitted to the GIA for grading, the lab said.

The article also noted that the HPHT technology used to grow gem-quality diamonds has improved rapidly in the last few years, and that it’s now being used to produce “many” melee-size diamond as well as large colorless single crystals.

Moses and Wang said in the article that one Russian company, New Diamond Technology, is reportedly able to grow multiple large gem-quality colorless diamond crystals in a single run, and that Jinan Zhongwu New Materials is utilizing similar technology.

New Diamond Technology is the Russian company that produced a 10.02-carat, F color diamond and a 5.03-carat fancy deep blue. An article about the blue diamond also will be in the upcoming edition of Gems & Gemology and was published online beforehand.

While the Jinan’s total production volume remains unclear, “it is undoubtedly significant, and capacity is likely to expand in the near future,” the article states. “This strongly suggests that even more large HPHT synthetic diamonds will be introduced into the jewelry industry.”

A GIA spokeswoman said any further details the GIA is able to share about Jinan Zhongwu New Materials will be included in the spring edition of Gems & Gemology.



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