HPHT (High Pressure High Temperature) is both a method of creating lab-grown diamonds and a treatment process used to enhance the color of natural and lab-created diamonds.
As a growth method, HPHT replicates the natural conditions deep in the Earth where diamonds form, using extreme pressure (over 1.5 million pounds per square inch) and temperatures exceeding 1,400°C. As a treatment, HPHT can transform brown or yellowish diamonds into colorless or fancy colored diamonds by altering their atomic structure.
HPHT lab-grown diamonds are real diamonds with identical properties to mined diamonds. The treatment must be disclosed on diamond certificates as it permanently affects the stone's characteristics.