Tourmaline is a complex mineral group that forms numerous end-members and solid solution members, some of which produce gem-quality crystals. Tourmalines are commonly found in pegmatites or secondary gem placer deposits. Tourmaline can display certain phenomena such as chatoyancy (cat’s eye) and piezoelectricity. Tourmaline is found in a wide variety of different colours: red and pink (rubellite), blue (indigolite), green (verdalite), yellow (tsilaisite), black. Famous varieties include bluish greenish Paraiba tourmaline, chrome tourmaline and watermelon tourmaline (zoned tourmaline). Mines are found in Brazil, Sri Lanka along with a range of African countries such as Madagascar, Mozambique, Zambia, Nigeria, Tanzania and Namibia. Certain tourmaline varieties can be treated to improve their colour.