Topaz is a silicate mineral of aluminium and fluorine with the chemical formula A12Si04(F,OH)2. Topaz crystallizes in the orthorhombicsystem, and its crystals are mostly prismatic terminated by pyramidal and other faces. lt is one of the hardest naturally occurring minerals (mohs hardness of 8) and his the hardness of any silicate) (i.e. silicon-based) minerals.
