autunite

{{Infobox mineral | name = Autunite | boxwidth = | boxbgcolor =#d2d75e | image = Autunite-69257.jpg | imagesize = | alt = | caption = Autunite from Daybreak Mine, Washington | category = Phosphate minerals | formula = Ca(UO2)2(PO4)2·10–12H2O |IMAsymbol=Aut | molweight = 986.26 g/mol | strunz = 8.EB.05 | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Pnma | unit cell = a = 14.0135(6), b = 20.7121(8), c = 6.9959(3) [Å]; Z = 4 | color = Lemon-yellow to sulfur-yellow, greenish yellow to pale green; may be dark green to greenish black | colour = | habit = Tabular crystals, foliated or scaly aggregates, and in crusts | twinning = Rare on {110} | cleavage = {001} perfect, {100} and {010} poor | fracture = uneven | tenacity = | mohs = 2–2.5 | luster = Vitreous – pearly | streak = Pale yellow | diaphaneity = Transparent to translucent | gravity = 3.1–3.2 | density = 3.15 | polish = | opticalprop = Biaxial (−) | refractive = nα = 1.553 – 1.555 nβ = 1.575 nγ = 1.577 – 1.578 | birefringence = δ = 0.003 | pleochroism = X = colorless to pale yellow; Y = Z = yellow to dark yellow | 2V = Measured: 10° to 53° | dispersion = | extinction = | length fast/slow = | fluorescence = Strong yellow-green fluorescence in UV; Radioactive | absorption = | melt = | fusibility = | diagnostic = | solubility = Soluble in acids | impurities = | alteration = Dehydrates in air | other = Pseudotetragonal for synthetic material, 25px Radioactive | references = }}

Autunite (hydrated calcium uranyl phosphate), with formula Ca(UO2)2(PO4)2·10–12H2O, is a yellow-greenish fluorescent phosphate mineral with a hardness of 2–. Autunite crystallizes in the orthorhombic system and often occurs as tabular square crystals, commonly in small crusts or in fan-like masses. Due to the moderate uranium content of 48.27% it is radioactive and also used as uranium ore. Autunite fluoresces bright green to lime green under UV light. The mineral is also called calco-uranite, but this name is rarely used and effectively outdated.