Diamond is the hardest mineral known, and only a diamond can cut another. The best quality diamonds are prized as gems.

Diamonds have very strong bonding between the particles. Each carbon atom has covalent bonds to four others. This forms a series of tetrahedral (four-sided pyramid) shapes. This structure is why diamonds are so hard.

Diamond burns in air at 990°C. If it is heated in an inert gas, it turns slowly into graphite at 1000°C and quickly turns to graphite at 1700°C.

Diamonds can be found in South Africa, Tanzania and the US. They are also mined from places such as Brazil, Zaire, Sierra Leone and India.

Synthetic diamonds are used in industry. They are made by applying very high temperatures and pressures to graphite.

Diamonds sparkle because they have a high refractive index (with a low critical angle) and they disperse light. The different colours of light have different refractive indices and refract and reflect at different angles.