The winter issue of GIA’s quarterly Gems & Gemology,    carries an article by Wuyi Wang,  GIA’s director of research and development and Billie “Pui Lai” Law, diamond grader at GIA’s Hong Kong laboratory, in which the authors have detailed the finding of an over 5 carat stone created by the use of Chemical Vapour Deposition (CVD) technology.

The authors say it is possible   to produce “large, high-quality near-colourless and colourless synthetic diamonds” as CVD technology has seen much improvement  in its techniques over the past  years.

 “Two samples over 3 carats were reported in early 2016 as the largest CVD synthetics,” the article  states. “GIA recently tested a CVD-grown synthetic diamond that weighed over 5 carats, marking a significant milestone.”

The authors add: “The 5.19 ct cushion modified brilliant measuring 10.04 × 9.44 × 6.18 mm (figure 1) was submitted to GIA’s Hong Kong laboratory for grading service. The stone was not disclosed as a synthetic diamond. Using the lab’s standard screening and testing processes, it was identified as CVD synthetic. Following examination, a GIA Identification Report was issued and the stone was inscribed on the girdle with the report number and the words “Laboratory Grown,” following GIA’s protocols for undisclosed synthetics.”

What  is noteworthy about  this finding is that not only was this   the largest CVD synthetic diamond examined by GIA  to date;  it is also the  largest reported in the jewellery industry.

“It had J-equivalent colour grade and VS2-equivalent clarity, comparable to a high-quality natural counterpart,” the authors report. “Natural-looking internal inclusions such as needles and clouds were the major features .  Strong graining and a fracture in the table were also clearly observed under the microscope. It is worth noting that black inclusions, often contained in synthetic diamond, were not found in this CVD specimen, which could have been mistakenly identified as natural based on microscopic examination alone. This case therefore highlights the importance of using advanced spectroscopic instruments as well as conventional gemmological techniques to ensure an accurate identification.”