On the chromite from the Hiroosa mine, Shizuoka Prefectore

The chromite bodies at the Hiroosa mine consist of massive chromite, of grains disseminated in serpentinite. In thin section the dusty magnetite and yellowish brown chlorite are abundant in darker variety of serpentinite, but in greenish serpentinite those are scarcity. Chromite in serpentinite rarely has black margins and is crossed by black opaque material, presumably ferrian chromite or chromian magnetite. Chromite samples analyzed by the present writer gave a content of CT2O3 ranging from 47 to 52% and Cr/Fe ratio of 1.7 to 2.1. It appears likely that there may be systematic variation from spinel molecule to magnetite molecule in composition of the chromite. It seems that FO2O3 is concentrated in the residual solutions.