Topaz

Topaz is a silicate mineral. Along with silicate, it includes the chemical elements aluminium and fluorine with the chemical formula Al₂SiO₄(F,OH)₂.

Topaz
Topaz crystal on matrix
General
Category	Nesosilicate
Formula (repeating unit)	Al2SiO4(F,OH)2
Strunz classification	9.AF.35
Crystal symmetry	Orthorhombic dipyramidal H-M symbol: (2/m 2/m 2/m) Space group: Pbnm
Unit cell	a = 4.65 Å, b = 8.8 Å, c = 8.4 Å; Z = 4
Identification
Color	Colorless (if no impurities), blue, brown, orange, gray, yellow, green, pink and reddish pink
Mohs scale hardness	8 (defining mineral)
Luster	Vitreous
Birefringence	δ = 0.010
References	[1][2][3][4]

Color and varieties

Pure topaz is colorless and transparent but they usually have colors made by small impurities. The typical topaz is wine, yellow, pale gray, reddish-orange, or blue brown. It can also be made white, pale green, blue, gold, or pink (rare).

Orange topaz, also known as precious topaz, is the traditional November birthstone, the symbol of friendship, and the state gemstone for the US state of Utah.^[5]

Imperial topaz is yellow, pink (rare, if natural) or pink-orange. Some imperial topaz stones can fade if they are exposed too much in the sunlight.^[6][7]

Blue topaz is the US state Texas' gemstone.^[8]

Mystic topaz is colorless topaz which has been artificially coated, making it rainbow-colored.^[9]

Gallery

• 
  Colorless topaz, Minas Gerais, Brazil
• 
  A cut blue topaz
• 
  A red topaz
• 
  Imperial Topaz Gem
• 
  Facet Cut Topaz Gemstones in various colors, including mystic.

Related pages

• List of birthstones