Improvements in diamond growth technology and methods have led to a noticeable increase in colorless synthetic gem diamonds in recent years. Concerns in the diamond industry focus on laboratory-grown diamonds not being properly disclosed or even being sold as natural stones. Through careful examination and analysis, gemological laboratories can separate natural from synthetic diamonds. Occasionally, however, fraud is involved in attempting to conceal a gem’s identity. The Carlsbad laboratory witnessed such an attempt.
On this occasion, a round brilliant cut (figure 1, left) was submitted for an updated diamond grading report. Its girdle was inscribed with an actual GIA report number issued in 2015 (figure 1, right). The older report was for a natural, untreated diamond and contained the following grading information: 1.74 ct, round brilliant cut, D color, Excellent cut grade, and VVS1 clarity. Upon grading, the new submission was described as a 1.76 ct round brilliant cut with F color, Excellent cut grade, and VS1 clarity. Moreover, our screening processes determined that the newly submitted sample needed additional testing to determine its origin. This examination revealed it to be an HPHT-grown synthetic diamond. Synthetic cuboctahedral growth structure and phosphorescence were clearly visible in DiamondView imaging (figure 2).
Figure 2. DiamondView imaging showed the synthetic growth structure and blue phosphorescence typical of HPHT-grown synthetic diamonds.
Aside from the observed discrepancies in weight (1.74 vs. 1.76 ct), color (D vs. F), and clarity (VVS1 vs. VS1), FTIR spectra clearly showed that these were not the same diamond. The natural diamond from the original report was type Ia with aggregated nitrogen impurities, while the new one was type IIb with boron impurities (figure 3). Careful examination of the report number inscribed on the synthetic diamond revealed a font different from the one used by GIA, proving that it was not an authentic inscription.
Figure 3. FTIR absorption spectra revealed that the synthetic diamond was type IIb, whereas the fraudulently inscribed report number referred to a natural type Ia diamond. The spectra are offset for clarity.
While most synthetic diamonds that come to the laboratory are properly disclosed, some are submitted out of concern that a stone presented as natural might be synthetic. Rarely do we encounter the type of blatant fraud described here. It is important for the industry and public to exercise caution, because these types of misleading practices do occur. We believe the submitting client noticed inconsistencies with the GIA report information and sent it to the lab for an updated report. If any doubt exists or some aspect of a diamond (such as an inscription) seems odd, the stone should be sent to a gemological laboratory for verification.
Source: GIA Education