The crystal structure of kelyanite, (Hg2)6(SbO6)BrCl2

Abstract

The crystal structure of kelyanite, a rare mercury mineral that was found in oxidized mercury-antimony ores in the Kelyana deposit (Buryatia, Russia), has been determined. The preliminary formula of kelyanite was Hg34Sb3Cl3Br1O28 (assuming the presence of both the Hg1+ and Hg2+). In contrast to this assumption, kelyanite appears to contain only monovalent Hg and its revised formula is (Hg2)6(SbO6) BrCl2. Kelyanite is trigonal, space group P 3, a = 13.560(4), c = 10.004(6) A, V = 1593(1) A3, and Z = 3. In the structure, Hg atoms form six crystallographically independent pairs [dumbbells of composition (Hg2)2+] with Hg-Hg distances of 2.482(3)–2.519(2) A. The Hg and O atoms form O-Hg-Hg-O systems with Hg-O bond lengths of 1.98(3)–2.33(3) A and HgHgO angles of 140.3(7)–168.3(9)°. Mercury atoms in the (Hg2)2+ dumbbells have additional coordination to O, Cl, and Br atoms [Hg-O 2.62(2) A, Hg-Cl 2.68(1)–2.97(1) A, and Hg-Br 3.00(1)–3.55(1) A]. Three crystallographically independent Sb atoms are octahedrally coordinated by O atoms with Sb-O distances of 1.96–2.14 A. The (Hg2)2+ dumbbells link the (SbO6) octahedra in a 3D structure.