The Gemological Institute of America (GIA) has announced that its Hong Kong laboratory recently identified an undisclosed chemical vapor deposition (CVD) grown diamond weighing 5.19 carats, the largest ever CVD synthetic diamond ever detected, "marking a significant milestone." GIA says that CVD technology has accelerated over the last several years, and the rapidly improving techniques have produced large, high-quality near-colorless and colorless synthetic diamonds. Two samples over 3 carats were reported in early 2016 as the largest CVD synthetics, but a 5-carat stone is unprecedented.
GIA states: "The 5.19 ct 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 jewelry industry." More worrying is the fact that the diamond in all respects resembles a natural diamond: "It had J-equivalent color grade and VS2-equivalent clarity, comparable to a high-quality natural counterpart. 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 gemological techniques to ensure an accurate identification."
Visit the GIA page linked to this article for a full description.