Hisingerite Occurring as a Weathering Product of Iron-Rich Saponite

Norihiko Kohyama and Toshio Sudo
Geological and Mineralogical Institute, Faculty of Science, Tokyo University of Education, Tokyo, Japan

Abstract: Hisingerite occurs as a weathering product of iron-rich saponite in rhyolitic tuff of Oya, Tochigi Prefecture. The chemical composition: SiO2, 40·68%; Al2O3, 4·44%; Fe2O3, 28·54%; MgO, 1·85%; CaO, 1·42%; Na2O, 1·50%; K2O, 0·33%; H2O+, 6·43%; H2O, 13·70%; total 98·89%. Very broad and weak X-ray powder reflections occur at 16, 4·5, 2·5, 1·7 and 1·5 Å, which correspond to the main peaks of nontronite. It is considered that trioctahedral iron-rich saponite was altered to hisingerite, a very poorly crystalline form of nontronite, by oxidation of iron and advanced leaching of octahedral Mg ions.

Clays and Clay Minerals; July 1975 v. 23; no. 3; p. 215-218; DOI: 10.1346/CCMN.1975.0230309
© 1975, The Clay Minerals Society
Clay Minerals Society (www.clays.org)