Type Ia | Type Ib | Type IIa | Type IIb | |
---|---|---|---|---|
Characteristics | Contain nitrogen atoms | Contain nitrogen atoms | No nitrogen impurities | Low levels of nitrogen impurities |
Market dominance | 98% | 0.1% | 1-2% | 0.1% |
Light absorption / Visible absorption spectrum | Blue | Green plus blue | None | Red, orange, yellow light |
Appearance | Pale yellow / almost colorless | Darker yellow / brown E.g. Canary yellow |
Colorless, almost or completely free from impurities | Light blue or grey, gradual absorption towards red spectrum |
Remarks | Type IaA atom arrangement does not affect diamonds’ colour; Type IaB gives yellow to brown tinge. | Almost all HPHT synthetics are Type Ib | Crystal inclusions are large and irregular; formed under extreme high pressure for longer time periods. E.g. Cullinan and Koh-i-Noor |
Contain significant boron impurities |