How Do You Know When Pink Is Really Natural Pink? – Oct.2005
Christopher Smith, director of Identification Services at GIA, gave a presentation on the identification of treated-color pink-to-red diamonds at a recent conference organized by the Accredited Gemologists Association (AGA).
Smith explained the distinguishing characteristics of HPHT-treated diamonds produced by Lucent Diamonds. The characteristics are:
· Areas around the girdle/pavilion that are not repolished after treatment show evidence of severe etching. Etch features were also evident in surface-reachiHow Do You Know When Pink Is Really Natural Pink?ng cleavages or fractures. Etching creates a coarse or granular appearance on the surface of the stones and along fracture walls.
· Surfaces of the diamond (both external and internal) surrounding included minerals along fractures to partially convert to graphite. The conversion to graphite requires about 30 percent more space, so internally, the resulting pressure it exerts may cause additional stress around included crystals or as extenstions of existing fractures.
· Purple and pink-to-red color concentrations often occurred with brown concentrations and regions that were near-colorless. No color concentrations were observed at the culet.
· Most commonly banded strain patterns were observed.
· Chalky fluorescence is exhibited to long-wave UV, usually in combinations of yellow, green, and orange. Under short-wave UV, they showed medium to strong orange fluorescence, commonly with weak yellow zones. Prominent green visible luminescence was typical. Orange-red and yellow visible luminescence was also detected.v