GE developed a process known as High Pressure High Temperature (HPHT) treatment to permanently enhance a rough diamond’s tinted color. This process is suitable primarily on higher-clarity diamonds or diamonds having specific criteria (about 1% of all gem quality diamonds). HPHT is an innovative procedure that brings out an imperfect diamond's true beauty and brilliance hidden by the natural imperfection of its color. 

These diamonds, which usually have a brown tint, are placed in an HPHT chamber and then treated with extreme temperature and high pressure which eventually changes the diamond’s molecular structure, significantly making them whiter in color.  This process is considered a permanent treatment and is almost impossible to detect without proper training, experience or equipment. 

The GIA uses very expensive equipment in order to determine if a diamond has undergone this kind of treatment.  If the treatment process is detected a note will be included on the diamond grading report for the buyer’s perusal.