Synthetic Moissanite with Fraudulent GIA Inscription

GIA Johannesburg recently received a 1.02 ct round brilliant for a Diamond Grading report. Standard testing showed it was not a diamond, and subsequent spectroscopic and gemological analysis proved it to be synthetic moissanite. We often encounter simulants submitted for diamond grading, and they are easily detected through the standard grading process. This near-colorless synthetic moissanite was noteworthy because it had a fraudulent GIA inscription. GIA checks all stones with a preexisting inscription, and this one was obviously not inscribed by GIA. The report number does belong to an E-color natural diamond graded in 2019 with the same weight. But because of the dissimilar SGs of diamond and moissanite (3.52 and 3.22, respectively), their measurements were quite different.

Synthetic moissanite (SiC) is sometimes mistaken for diamond because some of its properties approach those of diamond, namely hardness and thermal conductivity (a trait measured in some instruments to distinguish diamond from many other simulants). However, several other properties are quite different from diamond, such as a much higher dispersion (leading to more obvious fire) and double refraction. Nevertheless, the possibility exists that a consumer could purchase this simulant thinking it was a natural diamond, especially with a deliberately misleading inscription. In this case, careful examination protected the consumer against such attempted fraud.