Diamond types have a direct link to color enhancement treatments. Knowing the type of a diamond can help a gemologist to properly assess if a diamond has been treated or not. An article on this subject was published in the summer issue of Gems & Gemology by Christopher M. Breeding and James E. Shigley.

The different methods for growing and treating diamonds, which have been developed in the past few years, require sophisticated analysis and identification tools. The gemological laboratory aspires to tell the difference between a natural diamond that has undergone color enhancement and a synthetic diamond.

Colorless diamonds are usually divided into two types according to their transparency under UV and infrared fluorescence. Colorless diamonds are divided into Type I and Type II. This division is based on the presence or absence of nitrogen impurities in the diamond. A subdivision is performed according to the formation of nitrogen atoms in the diamond matrix, whether they are dispersed or clustered and the number of boron impurities in the diamond matrix. The diamond type allows/disallows treatment to enhance color through the use of a system incorporating high pressure and temperature.

The article lists the different types of diamonds and examines the connection between different diamond types and identification tools in the laboratory. In addition, the connection between a diamond type and synthetic diamonds was examined as well as the connection between diamond type and the geographical source of the diamond, the connection between diamond color and color change, and more.