16 Photos
Powellite
Chemical Formula	CaMoO4
Species	Molybdates & Tungstates
Crystal System	Tetragonal
Mohs Scale	3-4
Specific Gravity	4.255
Color	Yellow, brown, blue, black
Streak	light yellow
Luster	Sub-Adamantine, Resinous, Pearly
Refractive Index	n = 1.974 n = 1.984
Diaphaneity	Transparent, Translucent
Cleavage	Poor/IndistinctIndistinct on and .
Fracture	Irregular/Uneven
Crystal Habit：Massive to Crystalline
Geological Setting：Oxidation zone of hydrothermal deposits

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).