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Tungstite on ferberite.jpg
Bright yellow tungstite on ferberite
Category Mineral
(repeating unit)
Strunz classification 4.FJ.10
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Pmnb
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)

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.

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