Primary textures of manganese ores from the Sagadani mine, Ehime Prefecture, Japan

Abstract

Some primary ore-textures which are composed of rhodochrosite or caryopilite were observed in manganese ores from the Sagadani mine, where locates in the northern Chichibu Belt, Japan. The rhodochrosite ore shows lenticular form, which consists of spherulites representing cross extinction between crossed nicols. The textures of caryopilite ores are classified to three types. The first is isotoropically massive between crossed nicols, being the most common texture. The second is drop-like in mossaic quartz grains. The drops show homogeneous birefringence without internal textures. The third is a texture resembling peas in a pod or a fine string-like texture, which is inferred to be biogenic origin.
All the textures composed of rhodochrosite or caryopilite are presumed to be formed by diffusion of manganese ions into gelatinous materials of siliceous or muddy sediments.