Diamond Type is a method of scientifically classifying diamonds by the level and type of their chemical impurities. Diamonds are divided into two types as like Type I and Type II based on the presence or absence of nitrogen impurities.

Type I

  • Type I: contain nitrogen

    • Type Ia​

      • Type IaA​

      • Type IaB

    • Type Ib

  • Type II: not contain nitrogen

    • Type IIa​

    • Type IIb

Type I diamonds contain nitrogen atoms, either in aggregates(Type Ia) or in isolated atoms(Type Ib). When the nitrogen atoms are separated in pairs, they are designated TypeIaA, When they surround a vacancy, they are Type IaB. More than 95% of gem-quality diamonds are of the Type Ia.

Type IaA (N:nitrogen)

Type IaB (V:lattice vacancy)

Type Ia : aggregated N impurities

Type Ib: isolated N impurities

Type Ib

Type II

Type II diamonds have no measurable nitrogen impurities. Less than 2% of gem-quality diamonds are  'Type IIa'. These Type IIa diamonds are almost or entirely devoid of impurities, and consequently are usually colorless and have the highest thermal conductivity. Occasionally, while Type IIa diamonds are being extruded towards the surface of the Earth, the pressure and tension can cause structural anomalies arising through Plastic deformation during the growth of tetrahedral crystal structure, leading to imperfections. These imperfections can confer a yellow, brown, orange, pink, red or purple color to the gem. Type IIa diamonds can have their structural deformations 'repaired' by a HPHT(High Pressure and High Temperature) process, removing much or all of the diamond's color. Many famous diamonds,  like the Cullinan, Koh-i-Noor, Hope Diamond, and Lesedi La Rona, are Type IIa. Synthetic diamonds grown using the CVD process typically also belong to this Type IIa.

Type IIa

Type IIb (B is boron)

Diamond Type

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