powellite

{{Infobox mineral | name = Powellite | category = Molybdate minerals | boxwidth = | boxbgcolor = | image = Powellite-288824.jpg | imagesize = 260px | caption = | formula = CaMoO4 | IMAsymbol = Pwl | molweight = 200.02 g/mol | strunz = 7.GA.05 | system = Tetragonal | class = Dipyramidal (4/m) (same H-M symbol) | symmetry = I41/a | unit cell = a = 5.222 Å, c = 11.425 Å; Z = 4 | color = Straw-yellow, greenish yellow, yellow-brown, brown, colorless, may show blue to black zones | habit = Flat tabular crystals often paper-thin on {001}, may be crusty to pulverulent or massive | twinning = | cleavage = Indistinct on {011}, {112} and {001} | fracture = Conchoidal | tenacity = | mohs = 3.5-4 | luster = Adamantine | polish = | refractive = nω = 1.974 nε = 1.984 | opticalprop = Uniaxial (+) | birefringence = δ = 0.010 | dispersion = | pleochroism = O = blue; E = green | fluorescence = Fluoresces bright yellow under shortwave ultraviolet light, dimmer under longwave | absorption = | streak = light yellow | gravity = 4.25 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent | other = | 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 of 4.25. It forms a solid solution series with scheelite (calcium tungstate, CaWO4). It has refractive index values of nω=1.974 and nε=1.984.