Crystal structure of thoreaulite SnTa2O6

Torolyte-tin tantaloniobate according to chemical analysis has been earlier discussed as mineral with formula SnTa2O7 and tin of high valence. The problem arose to realize the lower valence Sn(2) and thus change chemical formula of torolyte: SnTa2O6. Coordination polyhedron around Ta(Nb) is a distorted octahedron with bond lengths varied from 1.83 to 2.21A, the ligands most remoted from the central atom composing common rib of two Ta(Nb) orthahedra. The Sn atom has two coordination spheres: the first includes 4 shorter Sn-O bonds (2.118-2.448A), the second involves 4 longer bonds (2.90-3.29A). The torolyte structure is based on parallel walls (100), double layers, of Ta(Nb) octahedra. Bivalent tin locates in the gaps of dense packing