Haruo Shirozu

Clay minerals associated with some manganese ore deposits

Three montmorillonites and a serjcite-montmorillonite regular mixed-layer mineral are described. The montmorillonites occur in the altered zone of the country rocks around the manganese-dioxide ore deposits, which were formed by the hydrothermal replacement in the tuffaceous rocks. They bear various colors, and (1) white and (2) brownishred masses from the Shiroiwa mine, Akita Prefecture, and (3) green one from the Miyazaki mine, Miyagi Prefecture, are mineralogically analyzed and shown that (1) and (2) are typical montmorillonite and (3) is beidellitic montmorillonite. The sericite-montmorillonite regular mixed-layer clay-mineral showing 25.2A spacing was found in a narrow fissure traversing the manganese ore deposit in the Paleozoic formation of the Aradani mine, Kyoto Prefecture. It associates with a large quantity of fine-grained bipyramidal quartz. X-ray, D. T. A. and chemical analyses along with heating-effect data show that the clay-mineral is a regular mixed-layer mineral having almost equal percentages of sericite and montmorillonite layers.