Topaz is a mineral aluminium fluosilicate occurring in rhombic prisms, generally yellowish and pellucid, also colourless, and of greenish, bluish, or brownish shades with a glassy lustre, fine varieties of the mineral are valued as gem stones. It sometimes occurs massive and opaque. Topaz is formed by fluorine-bearing vapours given off during the last stages of the solidification of igneous rocks and is frequently associated with tin stone, tourmaline, mica. beryl, etc. The deep orange yellow varieties of the mineral are most valued, and the finest stones have been found in the UralMountains and Brazil. Some of the Brazilian stones become pink on heating and are used in cheap jewellery. Topaz crystals are also found in Saxony, Scotland, Ireland, the south-west of England, Africa, India, Japan, North America, etc. Many so-called topazes are really only yellow varieties of quartz.Topaz has the formulae Al2SiO4(F,OH)2 and a relative hardness of 8. Research Topaz
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Rocks & Minerals
Research Topaz
