High pressure high temperature (HPHT) treatment has long been applied in the gem trade for changing the body colour of diamonds. The identification of HPHT-treated diamonds is a field of on-going research in gemological laboratories, as different parameters of treatment will result in either the cre...

The enhanced optical properties of chemical vapor deposited (CVD) diamond have been pursued in academia and industry for many applications. However, the barrier of CVD technology limits the application field of diamond. Herein, the performance of CVD polycrystalline diamond thick films was improved ...

Single crystal diamonds grown by chemical vapor deposition (CVD) before and after different post-growth treatments were studied using optical spectroscopy. The most pronounced changes in color were observed after irradiation with subsequent annealing at 800 °C whereas a weakening of gray tint took p...

This study of type IIa GE POL diamonds before and after HPHT annealing by GE significantly expands on their characterization. The color change was dramatic: from the N-O range through Fancy Light brown before, to D-H after. However, there was little change to the inclusions, graining, and strain as ...