gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1983.047.345.18 Ganophyllite from Franklin, New Jersey; Pajsberg, Sweden; and Wales: New Chemical Data Dunn Pete J. Department of Mineral Sciences, Smithsonian Institution, Washington, DC 20560, USA Peacor Donald R. Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA Nelen Joseph E. Department of Mineral Sciences, Smithsonian Institution, Washington, DC 20560, USA Ramik Robert A. Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, Canada 12 1983 47 345 563 566 28 9 1982 Copyright © 1983, The Mineralogical Society 1983 Abstract

Ganophyllite from Franklin, New Jersey, Pajsberg, Sweden, and the Benallt Mine, Wales, has been chemically reinvestigated. Twelve new analyses confirm the general structure of Kato (1980) and yield the tentative formula (K,Na,Ca)2Mn8(Si,Al)12(O,OH)32(OH)4·8H2O. There is little solid solution among octahedral cations, and the Si:Al ratio is nearly constant at 10:2. Ca and (Na + K) are apparently differentiated, but all examined ganophyllites are K-rich. Much of the water content is loosely bound and the upper limit of water content is not well defined. Ganophyllite is relatively invariant in chemical composition from locality to locality.