As part of our ongoing research for means to identify HPHT-annealed diamonds, the East Coast laboratory recently analyzed 11 pink and four blue diamonds that had been subjected to this process (see figure, © GIA). These diamonds were submitted to the laboratory from Bellataire Diamonds, which is responsible for marketing GE POL diamonds in the United States.

The diamonds weighed 0.75 to 14.93 ct. The pink diamonds showed a wide range of color saturation, from the equivalent of Faint to Fancy Deep; the blue diamonds ranged from the equivalent of Very Light to Fancy Intense. The clarity grades ranged from IF to VS₂ and from VVS₁ to VVS₂  for the pink and blue diamonds, respectively. The pink diamonds were type IIa, based on their mid-infrared spectra and their transparency to short-wave UV radiation. The blue diamonds were type IIb; that is, they showed both electrical semi-conductivity and characteristic boron features in the mid-infrared. According to Chuck Meyer, managing director of Bellataire Diamonds, the pink and blue diamonds represent a very small fraction of the overall GE POL production. Because of the rarity of the starting material that can generate these colors, he does not expect them to be readily available commercial items.

Gemologically, these HPHT-annealed diamonds show properties that are commonly observed in natural-color type IIa pink and type IIb blue diamonds, particularly the details of color zoning, and reactions to long-wave and short-wave UV. We would expect the same types of alteration of inclusions to occur as were previously reported for HPHT-annealed near-colorless type IIa diamonds (T. Moses et al., “Observations on GE-processed diamonds,” Fall 1999 Gems & Gemology, pp. 14–22), but these 15 diamonds did not show any diagnostic inclusions. Using a Raman unit, we obtained photoluminescence (PL) spectra on these HPHT-annealed pink and blue diamonds, which we compared to PL spectra for more than 100 natural-color pink and blue diamonds. It appears that some of the identification criteria proposed by D. Fisher and R. A. Spits (”Spectroscopic evidence of GE POL HPHT-treated natural type IIa diamonds,” Spring 2000 Gems & Gemology, pp. 42–49) to differentiate D-to-Z range GE POL diamonds from natural type IIa diamonds may be applicable in the identification of the HPHT-annealed pink diamonds. We are using this spectroscopic method and other techniques to investigate possible identification criteria for both the pink and blue diamonds.

Photo GIA