HPHT-Treated Type IIa Yellow Diamond

Wuyi Wang; Gelb, Thomas
March 2005
Gems & Gemology;Spring 2005, Vol. 41 Issue 1, p43
Academic Journal
The article discusses the gemological properties of a 4.33 carat cut-cornered rectangular modified brilliant cut similar to that associated with natural-color type Ia yellow diamonds commonly referred to as cape diamonds examined at the East Coast laboratory. The sample displayed very weak blue fluorescence to long-wave ultraviolet (UV) radiation and a very weak yellow fluorescence to short-wave UV, with no phosphorescence. The infrared absorption spectra showed features typical of a type IIa diamond, with no detectable A-form or B-form nitrogen. It is inferred that the sample proved to be a type IIa high pressure high temperature (HPHT)-treated diamond.


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