gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1959.032.247.01 The Fibrous Zeolite Erionite; Its Occurrence, Unit Cell, and Structure Staples Lloyd W. B.A., M.S., Ph.D. Head of Dept. of Geology, University of Oregon, Eugene, Oregon, U.S.A. Gard J. A. B.Sc., Ph.D. Dept. of Chemistry, University of Aberdeen, Scotland 12 1959 32 247 261 281 Copyright © 1959, The Mineralogical Society 1959 Summary

The type locality for erionite has been identified and specimens compared with Eakle's original material. New determinations of the physical properties and a chemical analysis have been made. Correlation of X-ray powder and fibre rotation data with electron diffraction of single crystals has shown that the unit cell is hexagonal with a 13·26, c 15·12 Å., space-group P31c, P¯31c, P63mc, P¯62c, or P63/mmc, giving a calculated sp. Gr. of 2·07 and atomic cell contents (Ca, Mg, Na2, K2)4·5Al9Si27O72.27H2O. A structure is proposed for the aluminosilicate frame, with space-group P63/mmc, which gives satisfactory correlation between observed and calculated structure factors for the X-ray fibre rotation pattern.