Tungstite

 Tungstite is a hydrous tungsten oxide mineral with formula: WO₃·H₂O. It is a secondary mineral formed by the weathering of other tungsten containing minerals. It crystallizes in the orthorhombic system in translucent yellow to yellow green masses. It is clay-like with Mohs hardness of 2.5 and a specific gravity of 5.5.

Tungstite
Bright yellow tungstite on ferberite
General
Category	Mineral
Formula (repeating unit)	WO3·H2O
Strunz classification	4.FJ.10
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pmnb
Identification
Formula mass	249.86 g/mol
Color	Yellow, yellowish green/orange
Crystal habit	Earthy, pulverulent
Cleavage	Perfect along [001], imperfect along [110]
Mohs scale hardness	2.5
Luster	Resinous, pearly
Streak	Yellow
Diaphaneity	Transparent
Specific gravity	5.517
Optical properties	Biaxial (-)
Refractive index	nα = 2.090, nβ = 2.240, nγ = 2.260
Birefringence	δ = 0.170
Dispersion	r < v (strong)

It was first described in 1868 for an occurrence near Trumbull, Connecticut at the Hubbard Tungsten Mine at Long Hill.

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.