The crystal structure of malayaite, CaSn0.95 Ti0.05 OSiO4 (A2/a; a = 7.149, b = 8.906, с = 6.667 A; β = 113.3°; Z = 4) has been refined to R = 0.047, using 872 non-equivalent reflections. Malayaite is topologically identical to P21/a titanite (CaTiOSiO4) and a number of rare arsenate and phosphate minerals, but it is truly isostructural only with the high-temperature (>220°C) form of chemically pure titanite. Kinked chains of vertex-sharing [SnO6] octahedra run parallel to a; these are bridged by [SiO4] tetrahedra in such a way as to form an [SnOSiO4]-2 framework with large cavities containing the Ca atoms in irregular 7-fold coordination.

The steric details of the malayaite structure are predictable in terms of classical Pauling principles. The mean bond lengths are Si-O = 1.641 A, Sn-O = 2.042 A, and Ca-O = 2.483 A.

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First page of The structure of malayaite, CaSnOSiO<sub>4</sub>, a tin analog of titanite
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