Diamond type
Diamond type is a method of scientifically classifying diamonds by the level and type of their chemical impurities. Diamonds are separated into four types: Type Ia, 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.
Gemological Institute of America
The GIA Laboratory provides a variety of gem grading and identification reports. Diamond grading reports for unmounted natural and synthetic diamonds determine their key characteristics: color, clarity, cut and carat weight. GIA issues two types of reports, the more complete being the Diamond Grading Report (a briefer and less expensive version is called a Diamond Dossier). The reports contain a number of measurements, including of carat weight as well as a diagram of where and what types of inclusions are located in the diamond. Diamond grading reports are now demanded by most consumers purchasing diamonds over a certain size, typically for over 0.5 carat (100 mg), and almost always for over 1.0 carat (200 mg), and are considered an important tool in guaranteeing that a diamond is accurately represented to a potential buyer.