Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay
Narsarsukite Na2(Ti,Fe+++)Si4(O,F)11 consists of paired double chains that might be better described as columns (purple). They are linked by titanium octahedra (blue). Sodium atoms (yellow) occupy voids between the titanium octahedra and the silica columns. The coordination polyhedra are irregular triangular prisms with a pyramid built out on one face (augmented triangular prism). The pyramids meet at a point, enclosing a square dimple into which the titanium octahedra fit. Four sodium polyhedra are shown below with the overlap with the titanium octahedra shown in green.
Above: Viewed down the c-axis, narsarsukite has tetragonal symmetry. Below: views normal to the c-axis. At left, the sodium atoms are shown as spheres, at right the coordination polyhedra are shown.
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Created 22 April 2013, Last Update