The Crystal Structure of Kalsilite, KAlSiO4

A. J. Perrotta and J. V. Smith
Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, U.S.A.

Summary: A full-matrix, three-dimensional refinement of kalsilite, KAlSi04 (hexagonal, a 5·16, c 8.69 Å, P6a), shows that the silicon and aluminium atoms are ordered. The respective tetrahedral distances of 1·61 and 1·74 Å agree with values of 1·61 and 1·75 Å taken to be typical of framework structures. As in nepheline, an oxygen atom is statistically distributed over three sites displaced 0·25 Å from the ideal position on a triad axis. This decreases the bond angle from 180° to 163° in conformity with observations on some other crystal structures. The potassiumoxygen distances of 2·77, 2·93, and 2·99 Å are consistent with the wide range normally found for this weakly bonded atom.

Mineralogical Magazine; December 1965 v. 35; no. 272; p. 588-595; DOI: 10.1180/minmag.1965.035.272.02
© 1965, The Mineralogical Society
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