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Adamas Gemological Laboratory

Transmittance Data on De Beers' Synthetic Diamonds

Courtesy of the Jewelry Council of South Africa Diamond Certification Laboratory and De Beers, Adamas Gemological Laboratory was given access to six round brilliant cut De Beers' synthetic diamond samples. These were tested on the Jewelry Council of South Africa Diamond Certification Laboratory's SAS2000 Spectrophotometer Analysis System. The transmittance data for these data are shown below.

Figure 1 shows transmittance data taken on sample SYN106-16, a 0.51ct yellow round brilliant cut synthetic diamond. The transmittance data is compared to an HRD certified Z master, the defined breakpoint between Z color and fancy yellows. Note the absence of the nitrogen absorption system (415nm, 430-480nm) characteristic structure shown in the Light Fancy Yellow Master, which is a typical "cape series" diamond.

Figure 2 illustrates the transmittance of a De Beers' synthetic Blue diamond, SYN93-4,  Type 2b, electrically conductive. It might be noted that you may be able to use your diamond thermal conductance tester as an indicator of Type 2b stones, as, to my knowledge, at least Presidium diamond testers sound a buzzer if they contact the hand held mounting. The electrical conductivity of Type 2b diamond is better than human tissue, which the current must pass through to initiate the buzzer warning.
Figure 2

Figures 3 and 4 show transmittance characteristics for two brown synthetics supplied by De Beers.

Figure 3
Figure 4
Figures 5 and 6 characterize the transmittance of two near colorless synthetic diamonds supplied by De Beers. Both lack the characteristics of the "cape series" masters shown for comparison.
Figure 5
Figure 6