A large garnet vein, associated chiefly with quartz and sparingly with hematite and epidote, occurs in dioritic rock forming Suisvô-yama in the Hida mountains. There are two kinds of garnet distinguishable in colour, greenish grey and wine-red, the former forming the main part of the mass and the latter appearing in a thin lining form in the cavities filled up by quartz which can be taken as the product formed by pneuma-tolytic action after the formation of the garnet mass. Hence the wine-red garnet is considered as a thermally altered variety of the greenish grey garnet. Main physical properties, namely, the index of refraction, specific gravity and cell-dimention, of the wine-red garnet were carefully deter-mined. For the refractive indices determined by the minimum deviation method for a crystal, three different values were obtained such as n_D=1.872, 1.881 and 1.890, owing to the zonal growth. The specific gravity and the cell-dimention are given as 3.831 at 4°C and 11.996 A respectively From these physical properties and the presence of MnO which was chemi-cally determined, the chemical composition of the garnet, calculated by. Kôzu's formula, can be given as And=87.34, Gr=4.75, Alm=3.54 and Sp=4.37%. The present studies were carried out under the guidance of Prof. S. Kôzu, to whom the author's hearty thanks are due.

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