THE CRYSTAL-STRUCTURE OF CHRISTELITE ZN3CU2(SO4)(2)(OH)(6)CENTER-DOT-4H(2)O

The crystal structure of christelite Zn3Cu2 .(SO4)(2)(OH)(6) . 4 H2O ( space group <P(1)over bar>; lattice parameters a = 5.4143(8) Angstrom, b = 6.336(1) Angstrom, c = 10.470(3) Angstrom,, alpha = 94.32(3)degre es, beta = 90.06(2)degrees, gamma = 90.27(2)degrees) was solved using direct methods and difference Fourier-syntheses. The structure was ref ined to a final R(F)-value of 0.033. The structure contains distorted [(Zn,Cu)O-6] octahedra which are connected as to form sheets of compos ition (2)(infinity)[(Cu,Zn)(2)(OH)(3)O](-), These sheets are similar t o those observed in the mineral ktenasite. In both structures sulphate groups are attached to the sheets of octahedra through common vertice s. In christelite the tetrahedral [SO4] groups are linked to isolated [Zn(H2O)(4)O-2] octahedra thus forming a three-dimensional structure, whereas in the structure of ktenasite the [SO4] tetrahedra are bonded to isolated [Zn(H2O)(6)] by a system of hydrogen bonds. The relationsh ip of christelite with other minerals is pointed out and discussed.