Diamonds are made of pure carbon in a crystallised form, although they often contain other minerals. Diamonds are usually clear, although they have a range of colours, such as pink, gold or blue, and are an excellent refractor of light.
Approximately 250 tonnes of ore must be dug from the ground to produce a one carat (200 milligram) polished diamond of gem quality. Diamond mines are open-cut or underground. The ore is blasted with explosives then loaded onto trucks for transport to a processing plant where it is cleaned and sorted.