- © 2008 American Mineralogist
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 P3, a = 13.560(4), c = 10.004(6) Å, V = 1593(1) Å3, 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) Å. The Hg and O atoms form O-Hg-Hg-O systems with Hg-O bond lengths of 1.98(3)–2.33(3) Å 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) Å, Hg-Cl 2.68(1)–2.97(1) Å, and Hg-Br 3.00(1)–3.55(1) Å]. Three crystallographically independent Sb atoms are octahedrally coordinated by O atoms with Sb-O distances of 1.96–2.14 Å. The (Hg2)2+ dumbbells link the (SbO6) octahedra in a 3D structure.