THE CRYSTAL-STRUCTURE OF DEANESMITHITE, HG1+(2)HG2+(3)CR6+O5S2

The crystal structure of deanesmithite, Hg21+Hg32+Cr6+O5S2, a 8.1287(8 ), b 9.4916(7), c 6.8940(4) Angstrom, a 100.356(6), beta 110.163(7), g amma 82.981(8)degrees, V 490.13(7) Angstrom(3), space group P (1) over bar, Z = 2, has been solved by direct methods and refined to an R ind ex of 2.9% on the basis of 2808 unique reflections measured with MoK a lpha radiation. There are six distinct Hg sites; two are at special po sitions on centers of symmetry. Hg(1) and Hg(2) form a diatomic Hg1+-H g1+ bond and are coordinated to additional S and O atoms. Hg(3) is in planar rhomb coordination with two S and two O atoms. The remaining th ree HE sites are each coordinated to six anions, forming distorted oct ahedra. The octahedra share edges to form corrugated sheets parallel t o (010), with one vacancy for every five occupied octahedrally coordin ated sites. The sheets are decorated on both sides by CrO4 tetrahedra that share faces with the vacant polyhedra and project in (approximate ly) the (010) direction. The heteropolyhedral sheets are held together by four-coordinated Hg(4) atoms and the Hg(1)-Hg(2) dimers. There are numerous similarities between the structures of deanesmithite and wat tersite, another Hg-bearing mineral from the Clear Creek claim.