Topaz

Topaz
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

Topaz is a silicate mineral. Along with silicate, it includes the chemical elements aluminium and fluorine with the chemical formula Al₂Si O₄(F,OH)₂.

↑ Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7
↑ Topaz. Handbook of Mineralogy. (PDF) . Retrieved on 2011-10-29.
↑ Topaz. Mindat.org. Retrieved on 2011-10-29.
↑ Topaz. Webmineral.com. Retrieved on 2011-10-29.