Austinite | |
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General | |
Category | Arsenate minerals |
Formula (repeating unit) | CaZnAsO4(OH) |
IMA symbol | Aus[1] |
Strunz classification | 8.BH.35 |
Dana classification | 41.5.1.3 |
Crystal system | Orthorhombic |
Crystal class | Disphenoidal (222) H-M symbol: (2 2 2) |
Space group | P212121[2] |
Unit cell | a = 7.43, b = 9.00 c = 5.90 [Å], Z = 4[3] |
Identification | |
Formula mass | 261.38 g/mol |
Color | Colourless, white to pale yellowish-white or bright green, colourless in transmitted light[4] |
Crystal 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}.[2] |
Twinning | Left- and right-handed individuals joined on {100}, with {010} and {001} coincident.[5] |
Cleavage | Good in two directions parallel to the prism faces {110}[2] |
Tenacity | Brittle |
Mohs scale hardness | 4 to 4.5 |
Luster | Subadamantine to silky in fibrous aggregates |
Streak | White |
Diaphaneity | Translucent to transparent |
Specific gravity | 4.12 |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.759, nβ = 1.763, nγ = 1.783, |
Birefringence | 0.024[2] |
2V angle | 47°[2] |
Dispersion | r > v weak |
Solubility | Easily soluble in cold dilute HCl[2] |
Other characteristics | Non-radioactive. Some austinite fluoresces green under SWUV. |
References | [4][6] |
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.[4] At one time “brickerite” was thought to be a different species, but it is now considered to be identical to austinite.[7] Austinite is named in honour of Austin Flint Rogers (1877–1957), American mineralogist from Stanford University, California, US.