HPHT diamond info posted on Ebay April 8, 2014
Did you know that Type II diamonds are the purest diamonds on the planet? Some of the whitest most beautiful diamonds ever discovered are Type II. The Cullinan diamond, the largest gem-quality diamond ever found, and the Kohinoor which is currently set into the Queen of England's Crown are both Type II. Type II diamonds are almost or entirely devoid of impurities and consequently are usually colorless.
Occasionally, while Type IIa diamonds are being extruded towards the surface of the Earth, pressure and tension can cause structural anomalies......leading to imperfections. These imperfections can confer a yellow, brown, orange, pink, red or purple color to the gem. Type IIa diamonds can have their structural deformations "repaired" via a high pressure high temperature (HPHT) process, removing much or all of the diamond's color.
In addition to changing Type II diamonds to white, HPHT can change various Type I diamonds from brown into striking fancy colors. Any diamond can be processed with HPHT but few diamonds achieve positive results. Included diamonds have a tendency to break during the process and diamonds with average chemistry will not yield pleasant fancy colors. Positive results of the HPHT process greatly depend on the existing chemistry and clarity inside each stone. Selection of proper material is critical.
We typically begin our HPHT processing regimen by examining thousands of stones. Diamonds of good clarity are chosen, stones with clarity imperfections are rejected.
Each stone is then individually scanned using an FTIR (Fourier Transform Infrared Spectroscopy). The spectrum tells us which diamonds will yield the finest colors.
Selcted stones are then sent to a facility for HPHT processing using a cubic press. In the HPHT press, dramatic molecular transformations occur. Color centers migrate and stress factors, long considered a cause of brown body color in diamond, can be eased. The diamond that once appeared as an unattractive brown stone emerges as a rare and beautiful white or fancy color. Mother Nature provides the building blocks and, using the best USA based technology, a process that began billions of years ago is brought to completion. Because the stones are scorched by the high temperature exceeding 2000 degrees, they must be polished before sale.
Our process may include one or several of the following: HPHT, irradiation and/or annealing to arrive at the final color. Each process is well disclosed to the customer.
Because less than 1% of the diamonds we test meet our selection standards there will always be limited quantities of premium goods available. However it is this painstaking process that provides hphtdiamonds.com's customers with an opportunity to possess something truly rare and unique.