The International Gemological Institute (IGI) has discovered a 6.18-carat synthetic diamond that fraudsters had misrepresented as natural by falsely pairing it with a mined-diamond grading report.

�This is the largest lab-grown diamond ever certified by a leading gemological laboratory where the sole purpose was to pass off a lab-grown stone as natural,� Bob Van Es, IGI managing director for Thailand and Hong Kong, said Wednesday.

A client submitted the round brilliant-cut loose stone to IGI�s Thailand lab for verification purposes. It came with a certificate from the Gemological Institute of America (GIA) for a natural, D-flawless diamond, but had in fact been cut with �meticulous precision� to match the data on that report, IGI noted. The stone was also inscribed with a fake GIA laser number corresponding to the certificate.

IGI has noted a rise in consumers sending diamonds to a second lab for checking, which can help avoid getting duped by fraudsters.

�At IGI, we have seen a huge increase in double-verification demand, which means before going for a major purchase, consumers like to receive confirmation that the stone matches the original report,� Van Es noted.

Image: Diamond grading. (International Gemological Institute)