ADAMAS GEMOLOGICAL LABORATORY publishes gemologically oriented software for the jewelry appraiser, jeweler, or student in gemology or mineralogy. The laboratory also provides technical consulting and jewelry appraisal services to the trade and the public and expert witness services to the legal profession.

The "Van Graff Diamond"

Just Another CZ?
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Adamas Gemological Laboratory  utililized the SAS2000 Spectrophotometer Analysis System to analyze a sample of "The Van Graff Diamond", a diamond simulant being sold on the internet as "itryium oxide" (Yttrium Oxide).

The gemological properties of the material as quoted from their promotional literature "Autheticity Certificate " are:

Material: Tempered Itryium Oxide
Hardness:  8.77 Mohs
Dispersion  0.080
Refraction  2.24
Specific Weight  5.72

Analysis

Using a linearly calibrated (Using Synthetic Spinel and Diamond) and specially modified dual range reflecting refractometer (The Jemeter Digital 90) we measured a refractive index of approximately 2.2x. The near colorless stone was singlely refractive. The stone was inert to long wave ultraviolet but had a weak greenish yellow short wave ultraviolet response. Based on a ratio calculation to diamond (we did not do a hydrostatic SG) the SG was approximately 1.70 times as dense as diamond for an SG of approximately 5.9x.  Thermal conductivity tests as a simulant. The stone is not electrically conductive. The Presidium Dual Tester read 058, which is in the CZ range. These properties were consistant with the tabulated properties of cubic zirconia (CZ). They were not consistant with published data on Yttrium oxide (Yttrolox).

From our memory of previous experiments we had run on Cubic Zirconia,  we searched our collection of colorless material and came up with 3 samples (out of 37) which showed a "rare earth" type of spectra, presumally due to trace amounts of some unknown "rare earth".  Two of these samples showed what we considered as IDENTICAL spectra to the "Van Graff Diamond", using both Vis-NiR and Photoluminescence spectroscopy.  One of the three CZ's showed a dissimilar "rare earth" spectra, and is shown below for comparison.
 
 

Visible - Near InfraRed Spectroscopy


 

SAS2000 LNIS (Liquid Nitrogen Immersion Spectroscopy)
Photoluminescence


 

Another CZ With Rare Earth Spectra
 


 

Conclusion

It appears to us that the "Van Graff Diamond" is nothing more than a Yttrium stabilized Cubic Zirconia !



 
 
 
 
 

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