Ashburtonite

Ashburtonite is a rare lead copper silicate-bicarbonate mineral with formula: HPb4Cu2+4Si4O12(HCO3)4(OH)4Cl.[4]

Ashburtonite
General
CategoryCyclosilicates
Formula
(repeating unit)		HPb4Cu4Si4O12(HCO3)4(OH)4Cl
Strunz classification9.CF.05
Crystal systemTetragonal
Crystal classDipyramidal (4/m)
H-M symbol: (4/m)
Space groupI4/m
Unit cella = 14.23, c = 6.1 [Å]; Z = 2
Identification
ColorBlue
Crystal habitPrismatic, needle like in clusters
CleavageNone
FractureConchoidal
TenacityBrittle
LusterVitreous to adamantine
Streaklight blue
DiaphaneityTransparent
Specific gravityGreater than 4.07, calculated 4.69
Optical propertiesUniaxial (+)
Refractive indexnω = 1.786 nε = 1.800
Birefringence0.0140
References[1][2][3][4]

Geological occurrence

Ashburtonite was first described as a secondary mineral in a shear zone in a series of shales and graywackes. It is an alteration product of galena and chalcopyrite.[3] The secondary minerals within the shear consist of carbonates, arsenates, and sulfates of lead and copper, and to a much lesser extent of zinc and iron.[4] Ashburtonite is associated with beudantite, brochantite, caledonite, cerussite, diaboleite, duftite, malachite, plattnerite, adamite, antlerite, bayldonite, bindheimite, carminite, chenevixite, chlorargyrite, chrysocolla, cinnabar, hemimorphite, hydrozincite, jarosite, lavendulan, linarite, mimetite, olivenite, paratacamite, and rosasite.

Ashburtonite was first described in 1991 for an occurrence in the Anticline prospects 11 km (6.8 mi) southwest of Ashburton Downs in the Capricorn Range of Western Australia.[3] It has also been reported from the Tonopah–Belmont Mine in the Big Horn Mountains of Maricopa County, Arizona.[2]

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References
  1. Webmineral
  2. Mindat
  3. Handbook of Mineralogy
  4. Grice, J. D.; Nickel, E. H.; Gault, R. A. (1991). "Ahsburtonite, a new bicarbonate-silicate mineral from Ashburton Downs, Western Australia: Description and structure determination" (PDF). American Mineralogist. 76: 1701–1707.


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