Tourmaline is one on the most complex gemstones of the silicate group. There are ten different varieties created by the dozen or more elements they contain. The origin of the term is the Sinhalese word "turamali", meaning stone of mixed colours. There are tourmalines, which change colour from daylight to artificial light. It is found in Africa, Brazil, Madagascar, Mexico, Myanmar, Namibia, Sri Lanka and USA.

Source: Encyclopedia of gemstones and minerals.