The crystal structure of cyanotrichite

摘要

We report the single-crystal average structure of cyanotrichite, Cu4Al2[SO4](OH)(12)(H2O)(2), from the Maid of Sunshine mine, Arizona, USA. Cyanotrichite crystallizes in space group C2/m, with the unit-cell parameters a = 12.625(3), b = 2.8950(6), c = 10.153(2) angstrom and beta = 92.17(3)(degrees). All non-hydrogen atoms were located and refined to R-1 = 0.0394 for all 584 observed reflections [F-o > 4 sigma F-o] and 0.0424 for all 622 unique reflections. The cyanotrichite structure consists of a principal building unit of a three-wide [Cu2Al(OH)(6)] ribbon of edge-sharing Cu and Al polyhedra || b, similar to that found for camerolaite. The ribbons lie in layers || (001) and between these layers, while SO4 tetrahedra and H2O molecules form rods running || b. A hydrogen-bonding scheme is also proposed.