Color Modification in HPHT-Annealed Diamonds
A broad range of colors is possible when exposing type ia brown diamonds to HPHT conditions. Depending on the reactions taking place internally, colors can be produced from deeply saturated orange to brownish-orange or brown-orange through pure yellow to slightly orange yellow, as well as greenish-yellow to yellowish-green. Photomicrograph by Christopher P. Smith, 10x.
In April 1999, the press release by Lazare Kaplan International (LKI) and General Electric (GE) announcing that they could successfully modify the color of certain diamonds, introduced the world to a new era in the diamond industry. A “new” high-tech color modification process had been revealed, which would have a profound effect on the diamond business. Up to that time, the trade had to contend with diamond color enhancements that were generally more readily detectable and rarely achieved a “natural-color” appearance (with the exception of some irradiation induced green colored diamonds.) Following investigations conducted by a number of gemological laboratories it became apparent that high pressure-high temperature technology (HPHT) was being applied to enhance the color of brown type iia diamonds.
The research was published in Rappaport in May of 2002.
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