Topaz is found colourless, bluish, yellow, pink, orange, brown and greenish in colour. It is commonly found in pegmatites and rhyolites. The most famous variety is orange to pink imperial topaz from Brazil. Blue topaz (Swiss Blue topaz and London Blue topaz) is commonly treated using irradiation to achieve the colour. Mines are found in Afghanistan, Brazil, Burma, Madagascar, Pakistan, Russia, Sri Lanka and Ukraine.