Type Ia: These diamonds contain nitrogen atoms in clusters. Approximately 95% of natural diamonds are type Ia. They normally vary from near-colorless to light yellow. These so-called “cape” diamonds derived their name from diamonds that were initially mined in or near Cape Province, South Africa.
Type Ib: These diamonds also contain nitrogen, but as isolated atoms instead of clusters. They are often bright yellow in color, and are extremely rare. The trade sometimes refers to these colors as “canary.”
Type IIa: These diamonds have no measurable nitrogen or boron impurities; they are usually colorless but they can also be gray, light brown, light yellow or light pink. Among all diamonds, those that are type IIa are chemically the most pure.
Type IIb: These diamonds are known to conduct electricity. The trace element boron is responsible for most diamonds that are blue or grayish blue in color.