AN INTERSTRATIFIED MINERAL OF MICA AND MONTMORILLONITE FROM THE MINERALIZED DISTRICT AT NIIDA NEAR THE SHAKANAI MINE, AKITA PREFECTURE, JAPAN

Abstract

An interstratified mineral of mica and montmorillonite was found in some drill cores at the Niida mineralized district near the Shakanai mine. The interstratification is produced by a two component stacking of about 60 9 mica-like layers and about 40 9 montmorillonite-like layers. The DTA curve shows double endothermic peaks for the dehydroxylation of the silicate layer. The infra-red data give 1 M illite and montmorillonite bands and band shifts, when heated to 500° and 550°C. Chemical composition: SiO₂ 47.13%; TiO₂ 0.33%; Al₂0₃ 31.76%; Fe₂O₃ 0.87%; MgO 0.35%; MnO trace; CaO 0.94%; K₂O 2.85%; Na₂O 0.04 9; H₂O+8.66 9; H₂0-6.97%; total 99.90%.