Powellite

"For Enoch Powell, see here. For his political philosophy known as Powellism, see here."Infobox mineral
name = Powellite
category = Mineral Species
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formula = CaMoO₄
molweight = 200.02 gm
color = Yellow, brown, blue, black
habit = Massive to Crystaline
system = Tetragonal - Dipyramidal
twinning =
cleavage = Distinct on the [111]
fracture = Conchoidal
tenacity =
mohs = 3.5-4
luster = Adamantine
polish =
refractive = n_ω = 1.974 n_ε = 1.984
opticalprop = Uniaxial (+)
birefringence = δ = 0.010
dispersion =
pleochroism =
fluorescence= None
absorption =
streak = light yellow
gravity =
density = 4.25 g/cm³
melt =
fusibility =
diagnostic =
solubility =
diaphaneity = Transparent
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references = [ [http://www.mindat.org/min-3275.html Powellite: Powellite mineral information and data ] ] [ [http://www.webmineral.com/data/Powellite.shtml Powellite Mineral Data ] ]

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.
* [http://webmineral.com/data/Powellite.shtml Webmineral data]
* [http://www.mindat.org/show.php?id=3275&ld=1&pho= Mindat with location data]
* [http://rruff.geo.arizona.edu/doclib/hom/powellite.pdf Mineral Data Publishing PDF]