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Abstract:

The crystal structure of sabinaite from Mont Saint-Hilaire, Quebec, has been refined to R 2.1 (a 10.196, b 6.616, c 17.958 Aa, beta 94.14 degrees , V 1208.2 Aa (super 3) , space group C2/c, with Z = 4). The structure indicates complete ordering of Zr (super 4+) and Ti (super 4+) and confirms that sabinaite is anhydrous; it is strongly layered and dominated by a slab composed of ZrO (sub 8) and TiO (sub 6) polyhedra. The ZrO (sub 8) polyhedra form infinite zig-zag chains along [100]; these are cross-linked along [010] by sharing polyhedral edges with similar polyhedra in adjacent chains and by sharing edges and corners with TiO (sub 6) octahedra that occupy gaps between the chains. The chains of ZrO (sub 8) polyhedra strongly influence the morphology and optical properties of sabinaite. Two distinct carbonate groups are present, one acting as a bidentate ligand in the ZrO (sub 8) polyhedra and the other linking vertices between ZrO (sub 8) and TiO (sub 6) polyhedra. The remaining oxygen atoms from these carbonate groups are shared with the NaO (sub 6) and NaO (sub 8) polyhedra and link the Zr-Ti-O slabs together along [001]; this bonding is relatively weak and results in the pronounced 001 cleavage seen in this mineral.

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GeoRef, Copyright 2018, American Geological Institute.<br/>2000-027836<br/>sabinaite<br/>SHELX-90