Chondrodite from Kamioka, Japan

Abstract

A new locality of chondrodite in Japan is found from a crystalline limestone included in. Inishi syenitic rock, near Kamioka Mine, Gifu Prefacture. The optical properties, the chemical composition of the chondrodite and the limestones in Inishi syenitic rock are given in the table 1, 2, 3, respectively. They show resemblance to G-chondrodite after H. von Eckermann. Chondrodite skarn here contains phlogopite, clinochlore, diopside, heden bergite, titanite, garnet, and secondary serpentine which replaced the chondrodite partly. A little quantity of dolomite is found accompanying with the chondrodite, but the limestones near the chondrodite locality is not dolomitic. One of the conspicuous characters of the chondrodite from Kamioka is the high content of MgO up to 57, 04 in weight percentage, as well as the poverty of FeO 1, 08%. Therefore the ratio MgO: FeO is about 57 which is a remarkably high value compared to the chondrodite from repre sentative localities in the world. The presence of chondrodite in Inishi syenitic rock and its extremely high ratio MgO; FeO bear some meaning on Hida metamorphism, i. e. the metamorphic differentiation seems to have taken place so completely in Inishi syenitic rock, that the Fe content was expelled out almost entirely from the roek, as well as from the chondrodite and their is formed “basic front” rich in Mg in the course of the granitization of Inishi syentic rock.