Mineral Composition of Manganese Ores from Yamato Mine, Fukushima Prefecture

The Yamato manganese deposits in biotite-granite found in Fukushima Prefecture, Japan, belong to epithermal fissure filling veins. In the upper zones of the deposits the ore consists of cryptomelane, pyrolusite, γ-MnO_2 and goethite, but in the lower zones, it consits of rhodochrosite and manganoan calcite. It is considered that the manganese dioxide minerals and goethite are altered from manganese carbonate minerals by weathering. The minerals of this mine were studied by means of X-ray powder method and differential thermal and chemical analyses. X-ray powder patterns of γ-MnO_2 in this mine are similar to those of γ-MnO_2 I by Cole et al. The chemical formula of rhodochrosite is (Mn_, Fe_, Ca_, Mg_) CO_3 and one of the most iron-rich rhodochrosite produced in Japan