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

The new mineral alumolukrahnite (IMA2022-059), CaCu2+Al(AsO4)(2)(OH)(H2O), was found at the Jote mine, Copiapo 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 similar 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 31/2. The mineral is brittle with irregular fracture and no cleavage. The calculated density is 4.094 g cm(-3). Optically, alumolukrahnite is biaxial (+) with alpha = 1.73(1), beta = 1.74(1) and gamma = 1.76(1) (white light). The empirical formula, determined from electron microprobe analyses, is Ca-1.01(Cu0.92Zn0.13)(Sigma 1.05)(Al0.96Fe0.01)(Sigma 0.97)(As0.985O4)(2)(OH)(0.88)(H2O)(1.12). Alumolukrahnite is triclinic, P (1) over bar, a = 5.343(5), b = 5.501(5), c = 7.329(5)angstrom, alpha = 67.72(2), beta = 69.06(2), gamma = 69.42(2)degrees, V = 180.3(3) angstrom(3) and Z = 1. Alumolukrahnite is a member of the tsumcorite group and is the Al analogue of lukrahnite.