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Powellite

For Enoch Powell, see here. For his political philosophy known as Powellism, see here.

Powellite
Category	Mineral Species
Chemical formula	CaMoO₄
Identification
Molecular Weight	200.02 gm
Color	Yellow, brown, blue, black
Crystal habit	Massive to Crystaline
Crystal system	Tetragonal - Dipyramidal
Cleavage	Distinct on the [111]
Fracture	Conchoidal
Mohs Scale hardness	3.5-4
Luster	Adamantine
Refractive index	n_ω = 1.974 n_ε = 1.984
Optical Properties	Uniaxial (+)
Birefringence	δ = 0.010
Ultraviolet fluorescence	None
Streak	light yellow
Density	4.25 g/cm³
Diaphaneity	Transparent
References	^[1]^[2]

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Powellite is a calcium molybdate mineral with formula CaMoO₄. Powellite crystallizes with tetragonal - dipyramidal crystal structure as transparent adamantine blue, greenish brown, yellow to grey typically anhedral forms. It exhibits distinct cleavage and has a brittle to conchoidal fracture. It has a Mohs hardness of 3.5 to 4 and a specific gravity is 4.34. It forms a solid solution series with scheelite (calcium tungstate, CaWO₄). It has refractive index values of nω=1.974 and nε=1.984.

Powellite was first described in 1891 in the Peacock Mine, Adams County, Idaho and named for American explorer and geologist, John Wesley Powell (1834-1902).

References

Palache, C., H. Berman, and C. Frondel (1951) Dana’s System of Mineralogy, (7th edition), v. II, pp. 1079–1081.
Webmineral data
Mindat with location data
Mineral Data Publishing PDF

Category: Oxide minerals