I was offered this beautiful diamond from one of my diamond dealers in Antwerpen last month. The diamond on the photo looks amazing, but it was originally an unattractive brownish color, and has been treated with HPHT (High Preasure, High Temperature), which makes the diamond into this beautiful colorless stone. Diamonds can also be treated with HPHT to become pink, blue or canary yellow diamonds.
HPHT treatment recreates the process that takes place deep inside the Earth's crust where diamonds were formed billions of years ago, to eliminate the structural disortations, that cause brownish coloring in some diamonds. The temperatures get as high as 2.600 degrees Celcius, together with high pressure, and the result is a colorless, pink, blue or yellow diamond.
The treatment is very difficult to detect, but all graded HPHT diamonds, will on the grading report have the little * after the color grade, with a note stating the treatment. An experienced diamond grader can detect the treatment when examining the diamond, if the diamonds has inclusions, these will normally change during HPHT treatment, and sometimes the enhanced diamonds will show hints of the original color when viewed from the side. Another point is that the HPHT treated diamonds tends to becomes magnetic and can be picked up by magnetic force.
Clients should always be told that the diamond is treated.
Prices on HPHT treated diamonds are much lower than non treated diamonds, up to 50 % cheaper. We don't see the same increase in prices of HPHT treated diamonds, as on non treated diamonds, so as an investment it is not optimal.
Did I buy the diamond? No, I didn't, but I am still considering.