Austinite

austinite

arsenate

conichalcite

hydrothermal

Images

Formula: CaZn(AsO₄)(OH)
Anhydrous arsenate containing hydroxyl, adelite-descloizite group, zinc-bearing mineral
Forms a series with conichalcite
Crystal System: Orthorhombic
Specific gravity: 4.13
Hardness: 4 to 4½
Streak: White
Colour: Colourless to pale yellowish white or bright green; colourless in transmitted light.
Solubility: Readily soluble in cold dilute hydrochloric acid (AM 20.112-119)

Hydrothermal environments

Austinite is a rare secondary mineral in the oxidised zone of some arsenic-rich base-metal deposits (HOM).

Localities

At the Lilli mine, Lomitos, Bolivia, austinite is associated with calcite and chalcedony (Dana).

At Bou Azzer, Morocco, austinite is found in quartz and dolomite cavities associated with roselite, cobalt-rich talmessite and calcite ((Minrec 38.5.361).
Austinite from Bou Azzer - Image

At the Brown Monster mine, Inyo county, California, USA, austinite has been found coating fracture surfaces with mimetite. (Minrec 41.2.181)

At the type locality, Gold Hill Mine, Tooele County, Utah, USA, austinite occurs in the oxidised zone of a metal deposit, associated with quartz, limonite, adamite and talmessite (Mindat, HOM). It is closely associated with adamite, and it appears to be a later mineral, since groups of crystals of austinite have been found coating and growing on top of the adamite (AM 20.112-119).
Austinite from the Gold Hill Mine - Image

Alteration

The Activity-pH diagram below was calculated at 298.2 K for some zinc arsenates and Ca₃(AsO₄)₂ for constant activity (roughly equivalent to concentration) of Ca²⁺ ions in solution, over a range of values of pH and of Zn²⁺ activity (MM 52.685).


The zinc mineral formulae are:
adamite: Zn₂(AsO₄)(OH)
köttigite: Zn₃(AsO₄)₂.8H₂O
austinite: CaZn(AsO₄)(OH)













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