austinite

{{Infobox mineral | name = Austinite | category = Arsenate minerals | boxwidth = 20 | image = Austinite-177832.jpg | imagesize = 260px | alt = | caption = Austinite from the Ojuela Mine, Mexico | formula = CaZnAsO4(OH) |IMAsymbol=Aus | molweight = 261.38 g/mol | strunz = 8.BH.35 | dana = 41.5.1.3 | system = Orthorhombic | class = Disphenoidal (222) H-M symbol: (2 2 2) | symmetry = P212121 | unit cell = a = 7.43, b = 9.00 c = 5.90 [Å], Z = 4 | color = Colourless, white to pale yellowish-white or bright green, colourless in transmitted light | habit = Well developed orthorhombic crystals of bladed or acicular habit elongated parallel to the c axis, sometimes with sceptre-like terminations, also radially fibrous crusts and nodules. Common forms are {110}, {111}, {1–11}, {010} and {011}. | lattice = | twinning = Left- and right-handed individuals joined on {100}, with {010} and {001} coincident. | cleavage = Good in two directions parallel to the prism faces {110} | fracture = | tenacity = Brittle | mohs = 4 to 4.5 | luster = Subadamantine to silky in fibrous aggregates | refractive = nα = 1.759, nβ = 1.763, nγ = 1.783, | 2V = 47° |dispersion= r > v weak | opticalprop = Biaxial (+) | birefringence = 0.024 | pleochroism = | streak = White | gravity = 4.12 | density = | melt = | fusibility = | diagnostic = | solubility =Easily soluble in cold dilute HCl | diaphaneity = Translucent to transparent | other = Non-radioactive. Some austinite fluoresces green under SWUV. | references = }} Austinite is a member of the adelite-descloizite group, adelite subgroup, the zinc (Zn) end member of the copper-Zn series with conichalcite. It is the zinc analogue of cobaltaustinite and nickelaustinite. At one time “brickerite” was thought to be a different species, but it is now considered to be identical to austinite. Austinite is named in honour of Austin Flint Rogers (1877–1957), American mineralogist from Stanford University, California, US.

==Structure== thumb|left|140px|Left-handed austinite thumb|left|140px|Right-handed austinite The structure is composed of chains of edge-sharing polyhedra ZnO6, and very distorted Ca(O,OH)8 polyhedra linked through AsO4 into a three-dimensional network.