The Gemological Institute of America (GIA) has recently tested a CVD-grown synthetic diamond that weighed over 5 carats.
The GIA reports that this marks a significant milestone. Chemical vapor deposition (CVD) technology has accelerated over the last several years, and the rapidly improving techniques have produced large, high-quality near-colourless and colourless synthetic diamonds. Two samples over 3 carats were reported in early 2016 as the largest CVD synthetics.
The 5.19ct cushion modified brilliant measuring 10.04 × 9.44 × 6.18 mm 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.
This is the largest CVD synthetic diamond GIA has examined to date, and 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 GIA says 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 gemological techniques to ensure an accurate identification.
CVD synthetics are available from several sources. The gemological and spectroscopic features of this 5.19 ct sample are very similar to those GIA has examined from Washington Diamonds (now known as WD Lab Grown Diamonds).
As diamond growth techniques continue to advance, the GIA expects to see more high-quality samples, both in size and clarity.