Austinite is a member of the

adelite The rare mineral adelite, is a calcium, magnesium, arsenate with chemical formula CaMgAsO4OH. It forms a solid solution series with the vanadium-bearing mineral gottlobite. Various transition metals substitute for magnesium and lead replaces cal ...

descloizite Descloizite is a rare mineral species consisting of basic lead and zinc vanadate, , crystallizing in the orthorhombic crystal system and isomorphous with olivenite. Appreciable gallium and germanium may also be incorporated into the crystal struc ...

group, adelite subgroup, the

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

(Zn) end member of the

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

-Zn series with

conichalcite Conichalcite, Ca Cu( As O4)(O H), is a relatively common arsenate mineral related to duftite ( PbCu(AsO4)(OH)). It is green, often botryoidal, and occurs in the oxidation zone of some metal deposits. It occurs with limonite, malachite, beudantite ...

. 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 Austin is the capital city of the U.S. state of Texas, as well as the seat and largest city of Travis County, with portions extending into Hays and Williamson counties. Incorporated on December 27, 1839, it is the 11th-most-populous city ...

(1877–1957), American mineralogist from Stanford University, California, US.

Structure

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.Gaines ''et al.'' (1997) Dana’s New Mineralogy Eighth Edition, Wiley Any

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

which has a

mirror plane In mathematics, a reflection (also spelled reflexion) is a mapping from a Euclidean space to itself that is an isometry with a hyperplane as a set of fixed points; this set is called the axis (in dimension 2) or plane (in dimension 3) of refle ...

as one of its symmetry elements has the property that its

mirror image A mirror image (in a plane mirror) is a reflected duplication of an object that appears almost identical, but is reversed in the direction perpendicular to the mirror surface. As an optical effect it results from reflection off from substances ...

(with any plane as the mirror plane) can always be superimposed on the original crystal by translation or rotation or both.
If there are no mirror planes as symmetry elements then the mirror image of a crystal cannot be brought into superposition with the original crystal by rotation or translation. This is enantiomorphism, and the mirror images are said to be enantiomorphs of each other. The possibility of enantiomorphic crystals is determined by the

crystal symmetry In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns th ...

, i.e., by the

point group In geometry, a point group is a mathematical group of symmetry operations (isometries in a Euclidean space) that have a fixed point in common. The coordinate origin of the Euclidean space is conventionally taken to be a fixed point, and every p ...

of the crystal species. There are 32 possible point groups, and 22 of these are capable of forming enantiomorphs. The enantiomorphs are designated right or left handed, according to whether they rotate the plane of

polarised light Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the ...

to the right or to the left. Sometimes it is clear from the outward form of the crystal whether it is right or left handed, and sometimes optical methods are needed to determine this. The commonest enantiomorphic mineral is

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

, with point group 32; all quartz crystals will be either right or left handed, but it may not be possible to distinguish this from the external form unless some critical crystal faces are present. Austinite has point group 222, with no mirror planes, so austinite is also an enantiomorphic mineral, occurring as both right handed and left handed crystals, with right handed ones more common.

Occurrence

Austinite is a rare mineral in the oxidation zone of arsenic bearing

base metal A base metal is a common and inexpensive metal, as opposed to a precious metal such as gold or silver. In numismatics, coins often derived their value from the precious metal content; however, base metals have also been used in coins in the past ...

deposits, where it is found developed on the colloform (pertaining to the rounded, globular texture of mineral formed by colloidal precipitation) surface of

limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·H2O, although this is not entirely accurate as the ratio of oxide to hydroxid ...

or lining small cavities. It is closely associated with

adamite Adamite is a zinc arsenate hydroxide mineral, Zn2 As O4O H. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Pure adamite is colorless, but usually it possess yellow color due to Fe compounds a ...

, and appears to be a later mineral. Austinite is associated with adamite,

, talmessite and limonite. Its type locality is Gold Hill Mine (Western Utah Mine), Gold Hill, Gold Hill District (Clifton District), Deep Creek Mts, Tooele County, Utah, US United States.

References

{{Reflist Arsenate minerals Orthorhombic minerals Minerals in space group 19