A FERRIC CELADONITE IN AMYGDALES OF DOLERITE AT TAIHEIZAN, AKITA PREFECTURE, JAPAN

Abstract

Celadonite, a green coloured mica clay mineral, is found in amygdales of altered dolerite at Taiheizan, Akita Prefcture. The specimen gives basal reflections at about 10Å and its submultiples, and its crystal structure is identified as a 1M polymorph from powder diffraction data. Although a DTA curve shows a small endothermic peak at about 100°C, the 10Å reflection was not affected either by heat treatment or by saturation with organic liquids. An infra-red spectrum is similar to that of a ferric celadonite reported by Farmer and Russell (1963). Chemical composition: Si0₂ 50.84%; TiO₂ trace; Al₂O₃ 5.08; Fe₂O₃ 19.35%; FeO 2.28%; MnO trace; MgO 6.10%; CaO trace; Na₂O 1.24%; K₂O 8.75%; H₂O⁺ 4.48 96; H₂O^-0.85%; total 98.97%.