MAGI Application note:

Detecting HPHT treatment of natural type IIa colorless diamonds

Sep. 3. 2013 Mikko Åström, Alberto Scarani, Marco Torelli

HPHT (High Pressure High Temperature) treatment can be used to enhance the color grade of brownish or grayish type IIa diamonds to colorless or near colorless. Most of the larger HPHT-treated diamonds has been sold branded as GE-POL, Bellataire, Pegasus or Monarch and can be readily identified by laser inscription located on the girdle of the stone. Unfortunately it is possible to remove these laser markings by repolishing the girdle, and small stones may have entered the market without any inscription at all. 

Photoluminescence spectroscopy is one of the very few methods available for determining HPHT treatment of colorless type IIa diamonds. However, this method can not be used alone without other instrumentation, because as a preliminary requirement, the sample under study has to be determined as natural type IIa diamond.

Important note: This application note applies only to colorless or near colorless diamonds.   Partially repolished "HPHT-processed"-inscription on the girdle of type IIa natural HPHT treated diamond.


Inga A. Dobrinets, Victor G. Vins, Alexander M. Zaitsev (2013) HPHT-treated Diamonds, ISBN 978-3-642-37489-0

We highly recommend this new publication for every gemologist interested about deep understanding of HPHT- treatment and it's detection. The book is in our opinion the most comprehensive review of dispersed publications written in past 15 years.

Further reading

GE-POL Diamonds: Before and After,   Christopher P. Smith, George Bosshart, Johann Ponahlo, Vera M. F. Hammer,
Helmut Klapper, and Karl Schmetzer
- Gems and Gemology, fall 2000, PP-192/215