Which Diamonds are Suitable for the HPHT Process

Not all natural diamonds are perfect candidates for HPHT processing. In fact, Type IIa is a unique breed, constituting only 2% of all natural diamonds. They are so highly regarded that a special GIA certification is awarded to Type IIa diamonds to accredit their exceptional color and brilliancy.

What are Type IIa diamonds? Experts classify diamonds into groups to indicate slight differences in their molecular structure. For instance, Type I diamonds —which make up the overwhelming majority of diamonds mined worldwide— are identified as stones that contain a natural nitrogen impurity. 

On the other hand, Type IIa diamonds —which are very rare— have a perfect molecular structure and very low nitrogen content. Some of them, in their natural state display a low color and when submitted to HPHT process they have the potential to become colorless and reach a very high color. Many of worldly known diamonds, such as Cullinan and Koh-i-Noor, are Type IIa.

Driven by our passion to salvage them, we are tirelessly searching for these inherently superior stones that prematurely emerged from volcanos and have the potential to turn into a "swan".

Special equipment, like a spectroscope and screening device, are necessary in determining the difference in types and whether or not the diamond meets the challenge of the HPHT process. Type IIa diamonds do not show signs of nitrogen impurities as seen through a Fourier-Transform Infra Red spectroscopy. Other tests include deep UV fluorescence examination with a DiamondView, or a similar device, photoluminescence studies at room temperature, and careful liquid nitrogen immersion with a Raman spectrometer.