gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1969.037.285.06 Further Detail on the Crystal Structure of Zussmanitc Lopes-Vieira A. 1 Zussman J. 2 Department of Geology and Mineralogy, Parks Road, Oxford

Now at Lab. de Technicas Fisico-Quimicas, Junta de Invest. do Ultramar, Alameda D. Alf. Henriques, 41-4 Esq. Lisbon, Portugal.

Now at the Department of Geology, The University, Manchester 13, England.

 3 1969 37 285 49 60 14 6 1968 Copyright © 1969, The Mineralogical Society 1969 Summary

Mineral data and a brief outline of the structure for zussmanite (ideal formula KFe13Si17AlO42(OH)14)have been published previously. This paper describes the determination of the crystal structure and presents and discusses the results. The structure consists of rhombohedrally stacked layers of Fe-(O,OH) octahedra to each side of which are attached rings of six (Si,Al)-O tetrahedra. These composite layers are linked to one another by rings of three (Si,Al)-O tetrahedra, and by potassium atoms, the latter in positions analogous to those in a mica. There is some evidence of disorder of the layer stacking. Interatomic distances and angles, and valency balance, are discussed.