The International Gemological Institute (IGI) recently analysed a 6.01-carat pear-cut gemstone with a grading report number inscribed on the girdle corresponding to a natural diamond but concluded that it was a lab-grown diamond. That lab grown stone’s carat weight, physical spread, and primary qualities were a close match with the natural diamond’s online grading data, said IGI.
While the main qualities of the stone paralleled the online report data the inscription pointed to, IGI’s gemmologists soon deduced that it was lab created. Photoluminescence spectroscopy revealed a doublet at 737 nm due to Silicone Vacancy (SiV) defects, indicating laboratory growth using the Chemical Vapor Deposition (CVD) process. This was further supported by microscopy, which showed a carbon inclusion in place of the feather indicated online, and a cloud, which would result in a lower clarity grade from IGI. A slight depth mismatch was also revealed. Such discrepancies could go unnoticed outside of a laboratory, particularly once the stone is set into a piece of jewellery.
Tehmasp Printer, CEO of IGI, said: “Everyone in our industry must be vigilant. IGI pioneered the grading of lab-grown diamonds nearly two decades ago for the purpose of clear separation from natural stones. As attempted fraud increases, the need for ongoing verification is a necessary step to protect consumers from purchasing misrepresented gems and jewellery.”
According to IGI, the client submitted the stone for screening, to determine whether it was natural or not. Additionally, per IGI policy, a laser-inscription with the LG prefix was added to the stone to clearly identify it as laboratory grown. A written statement was also issued to the client, so they may take it forward.
The discovery of the fraudulent stone comes on the heels of a number of other industry alerts that lab-grown are being sold as natural, the IGI added. (Photo courtesy: IGI)
11-01-2024
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