The 2020 Falls Edition of GIA’s Quarterly Journal, Gems & Gemology released in mid-January reported a sensational news of the discovery for the first time of a fradulent GIA inscription on a diamond simulant Moissanite, at their Johannesburg Laboratory in South Africa.
The diamond simulant was presented to the GIA Johannesburg Laboratory as a 1.02-carat, round brilliant-cut diamond requesting for a Diamond Grading Report. Standard procedure followed in testing the diamond showed that the stone was not a diamond at all. Further spectroscopic and gemological analysis revealed that the stone was in fact a synthetic moissanite, a common diamond simulant.
GIA reports that their laboratories often encounter simulants submitted for diamond grading, which are easily detected after subjecting them to the standard grading process. However, this simulant, a near-colorless synthetic moissanite was exceptional as it had a fraudulent GIA inscription, the first time such an inscription was detected on a diamond simulant. As a routine, GIA says, all stones with a pre-existing inscription are subjected to careful scrutiny and it was revealed that the inscription in this case was obviously not inscribed by GIA. However, the report number coincided with the number assigned to an E-color natural diamond with the same weight, graded in 2019, but due to the differences in the specific gravities of diamond and moisannite, which are respectively 3.52 and 3.22, the dimensions of the two stones were entirely different.
Apart from this the font of the fraudulent inscription was distinctly different from the font of the GIA’s standard inscription. As such, in keeping with GIA’s standard procedure, followed when such fradulent practices are detected, GIA superimposed characters to obscure the original fradulent inscription.
There was also a discrepancy in respect of the clarity grades. While the graded natural diamond had a clarity grade of VVS-1, if such clarity grade was assigned to the synthetic moissanite it would have been equivalent only to a clarity grade of VVS-2.
While the synthetic moisannite did not have any distinguishing inclusions, it did show the characteristic double refraction exhibited by moissanites under the microscope which imparted more fire to the stone than natural diamonds. Both the Infra-Red Absorption Spectrum and the Raman Spectrum cofirmed the identification as synthetic moissaite.
GIA also reports that several such instances of fraud had been detected as of recent times. One was in 2017 when a simulant resembling a natural rough diamond octahedron was identified as a synthetic moissanite. In the same year a lab-grown HPHT diamond was submitted with a fraudulent inscription also corresponding to another natural diamond. However, according to the GIA this is first time they have detected a fraudulent inscription on a diamond simulant.
Some of the properties of Synthetic Moissanite (SiC) and Diamond (C) are very close, such as hardness and thermal conductivity. While diamonds have the highest hardness of 10 on the Mohs scale, the hardness of Synthetic Moissanite is 9.00 – 9.50. Diamonds are among the most efficient thermal conductors. Synthetic Moissanite also has good thermal conductivity like diamonds. However, Moissanite has a higher Dispersion (0.104) than Diamonds (0.044) and Moissanites exhibit double refraction with Refractive Indices of 2.654 and 2.967, but diamonds exhibit only single refration with a Refractive Index of 2.417. Hence Moissanites have more fire and brilliance than Diamonds, that can mislead prospective customers. Thus the possibility exists that a consumer could unknowingly purchase the simulant thinking that it is a natural diamond, and especially when there is a deliberately misleading inscription. Thus in this case careful examination by GIA protected the consumer against attempted fraud.