Powellite

For the political philosophy of Enoch Powell, see Powellism.

Powellite
Yellow-honey powellite crystal with colorless needles of scolecite, from Yeola, Nasik, Maharashtra, India (size: 108 x 75 mm, 272 g)
General
Category	Molybdate minerals
Formula (repeating unit)	CaMoO4
Strunz classification	07.GA.05
Identification
Formula mass	200.02 g
Color	Yellow, brown, blue, black
Crystal habit	Massive to coarsely crystalline
Crystal system	Tetragonal - dipyramidal
Cleavage	Distinct on [111]
Fracture	Conchoidal
Mohs scale hardness	3.5-4
Luster	Adamantine
Streak	light yellow
Diaphaneity	Transparent
Density	4.25 g/cm3
Optical properties	Uniaxial (+)
Refractive index	nω = 1.974 nε = 1.984
Birefringence	δ = 0.010
Ultraviolet fluorescence	Fluoresces bright yellow under Shortwave ultraviolet light, dimmer under Longwave
References

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 by William Harlow Melville in 1891 from 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

External links

Media related to Powellite at Wikimedia Commons