The high-tech process has the power to transform the least valuable colored diamonds into the most valuable. That may explain why, after 12 years, it still makes the market uneasy.Twelve years ago this summer, the HPHT (high pressure/high temperature) process was introduced to the diamond industry, sparking what GIA then-president William E. Boyajian called “the biggest gemological crisis” in his 23 years at the Institute. At the 1999 GIA Symposium, an uproar erupted over the then-­undetectable treatment and its potential to capsize consumer confidence. Since then, the diamond industry has coped with far more serious crises, and HPHT has remained mostly a nonissue. And while it’s no longer considered undetectable and has yet to generate any negative publicity for the industry, HPHT is still viewed warily by a good portion of the trade. GIA recently shocked the industry by announ