Arizona porphyry copper/hydrothermal deposits I. The structure of chenevixite and luetheite

The crystal structure of chenevixite, Cu2M2(AsO4)(2)(OH)(4) (where M = Fe3 or Al), pseudo-orthorhombic, monoclinic, a = 5.7012(8), b = 5.1801(7), c = 29.265(2) Angstrom, beta = 89.99(1)degrees, V = 864.3(4) Angstrom(3), spac e group B12(1)1, Z = 4, was solved by direct methods and refined by least-s quares techniques to R = 8.4% and a goodness-of-fit (S) of 1.37 for 1176 un ique observed (F greater than or equal to 4 sigma(F)) reflections collected for a twinned microcrystal using graphite-monochromated Mo-K alpha X-rays and a CCD area detector. Vertex- and edge-sharing arsenate tetrahedra, Al p hi(6) octahedra, and Jahn-Teller-distorted Cu(2+)phi(6) octahedra [phi: O2- , (OH)(-)] form a framework unique from those in Cu2+ oxysalt minerals. Cha ins of edge-sharing Cu(2+)phi(6) octahedra, with Al phi(6) octahedra attach ed on opposing sides by the sharing of edges, are linked into layers parall el to (001) by sharing vertices with AsO4 tetrahedra, and the layers are li nked to form a framework by the sharing of polyhedral elements between adja cent Al phi(6) octahedra, as well as between AsO4 tetrahedra and Al phi(6) octahedra.