Any of the gem varieties of corundum except ruby, especially the blue variety, but other colours of sapphire include yellow, brown, green, pink, orange, and purple. Sapphires are obtained from igneous and metamorphic rocks and from alluvial deposits. The chief sources are Sri Lanka, Kashmir, Burma, Thailand, East Africa, the USA, and Australia. Sapphires are used as gemstones and in record-player styluses and some types of laser. They are synthesized by the Verneuil flame-fusion process. The intense colour of blue sapphire arises because of charge transfer involving titanium and iron ions, which are present as impurities. Because charge transfer is involved, the colour is visible even for very low concentrations of these ions.