Vermiculite from Ononii-machi, Fukushima Prefecture

Abstract

The vermiculite occured in neighbours of Ononii-maehi, Fukushima Prefecture was produced by alteration of the biotite, one of the constituent minerals of hornblende-biotite-granite. The vermiculite has a characteristic features to compare with foreign one. Namely SiO₂, Fe₂O₃ and CaO are much more contents. But MgO and H₂O are very little. This vermiculite was produced by metamorphism of biotite that FeO changes to Fe₂O₃ and it caught a large quantity of the secondary water of crystallization.