Identification and characteristics of PHT ('HPHT') – treated sapphires – An update of the GRS research progress

A series of peculiar events that commenced in 2015 brought a degree of uncertainty to the Sri Lankan gemstone industry. Sri Lanka is known as the world’s foremost producer of ‘heated’ corundum. So far only corundum of higher clarity has been used to produce clean sapphires. It was noticed that a few buyers began purchasing previously ‘untreat- able’ rough at uncommonly high prices. A rumor spread that a new treatment was developed and fears emerged that a new type of diffu- sion treatment could be responsible. Shortly afterwards some sapphire vendors were selling ‘heated’ sapphires below the already decreasing market prices of heated sapphires, and rumors were confirmed that a new type of sapphire treatment had been discovered. While speculations that HPHT-treated sapphires being responsible for the price decrease of heated sapphires are unsubstantiated, it can not be ignored due to the coincidental occurrence of events. The appearance of this new treatment came at a critical time of political and economical changes in Asia. If it did not negatively affect the market, it surely did not help.