THE CRYSTAL-STRUCTURE OF PINCHITE, HG5CL2O4

The crystal structure of pinchite, Hg5O4Cl2, a = 11.619(3), b = 6.105( 2), c = 11.710(3) angstrom, V = 830.6(4) angstrom3, space group Ibam, has been solved by direct methods and refined to an R index of 3.0% us ing MoKalpha X-ray data. There are three distinct Hg positions: Hg1 is coordinated by two O and four Cl atoms in a distorted octahedral arra ngement; Hg2 is coordinated by four O and two Cl atoms in a bi-diminis hed, Siamese dodecahedral arrangement; and Hg3 is coordinated by four O atoms in a distorted tetrahedral arrangement. The structure consists of layers of HgCl and Hg3O4 composition and is closely related to the structure of terlinguaite, Hg2+Hg2(2+)O2Cl2.