Diamond type is a method of scientifically classifying diamonds by the level and type of their chemical impurities. Diamonds are separated into five types: Type IaA, Type IaB, Type Ib, Type IIa, and Type IIb. The impurities measured are at the atomic level within the crystal lattice of carbon atoms and so, unlike inclusions, require an infrared spectrometer to detect.[1]
Different diamond types react in different ways to diamond enhancement techniques. Different types can coexist within a single stone; natural diamonds are often mixes of Type Ia and Ib, which can be determined by their infrared absorption spectrum.[2]