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Alumolukrahnite, CaCu2+Al(AsO4)2(OH)(H2O), the aluminium analogue of lukrahnite from the Jote mine, Copiapó Province, Chile

Published online by Cambridge University Press:  28 December 2022

Anthony R. Kampf*
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA
Stuart J. Mills
Affiliation:
Geosciences, Museums Victoria, GPO Box 666, Melbourne 3001, Australia
Barbara P. Nash
Affiliation:
Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA
Maurizio Dini
Affiliation:
Central University of Chile, La Serena, Chile
Arturo A. Molina Donoso
Affiliation:
Chilean Minerals, Iquique, Chile
*
*Author for correspondence: Anthony R. Kampf, Email: akampf@nhm.org

Abstract

The new mineral alumolukrahnite (IMA2022–059), CaCu2+Al(AsO4)2(OH)(H2O), was found at the Jote mine, Copiapó Province, Chile, where it is a secondary alteration phase associated with conichalcite, coronadite, gypsum, olivenite, pharmacosiderite, rruffite and scorodite. Alumolukrahnite occurs as crude diamond-shaped tablets up to ~0.1 mm, intergrown in crude spherical aggregates. Crystals are apple green and transparent to translucent, with vitreous lustre and a white streak. The Mohs hardness is 3½. The mineral is brittle with irregular fracture and no cleavage. The calculated density is 4.094 g cm–3. Optically, alumolukrahnite is biaxial (+) with α = 1.73(1), β = 1.74(1) and γ = 1.76(1) (white light). The empirical formula, determined from electron microprobe analyses, is Ca1.01(Cu0.92Zn0.13)Σ1.05(Al0.96Fe0.01)Σ0.97(As0.985O4)2(OH)0.88(H2O)1.12. Alumolukrahnite is triclinic, P$\bar{1}$, a = 5.343(5), b = 5.501(5), c = 7.329(5) Å, α = 67.72(2), β = 69.06(2), γ = 69.42(2)°, V = 180.3(3) Å3 and Z = 1. Alumolukrahnite is a member of the tsumcorite group and is the Al analogue of lukrahnite.

Type
Article
Copyright
Copyright © The Author(s), 2022. Published by Cambridge University Press on behalf of The Mineralogical Society of Great Britain and Ireland

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Footnotes

Associate Editor: Irina O Galuskina

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