What are HPHT-treated diamonds?
HPHT, which stands for high pressure/high temperature, is a laboratory process that can change the color in some gem diamonds. In the 1990s, scientists began to experiment with ways to modify diamond color using this technique. HPHT treatment can change the color of certain type IIa diamonds, making them colorless, pink or blue. HPHT can also change certain type Ia diamonds to green, yellowish green or yellow. Type IIa diamonds are very rare in nature, making up less than 2 percent of all diamonds mined Type Ia diamonds are the most abundant kind of diamond in nature.
