Hematite in pyrophyllite ore deposits, Shobara district, southwestern Japan

Hematite is a characteristic mineral of Liesegang rock in the pyrophyllite ore deposits, Shobara district, southwestern Japan. The mineral intimately coexists with fine-grained pyrophyllite and quartz. The hematite crystals a re characteristically needle-shaped to fibrous, and several microns in leng th, and can only be observed by high-magnification reflected light microsco py with oil immersion lens. They occur as ring-shaped aggregates several te ns of microns in diameter. Moreover, the crystals are often arranged radial ly within the rings. Microprobe analyses reveal that hematite crystals are almost pure iron oxid e, with less than 0.9 wt.% Ti. X-ray powder diffraction patterns and reflec tion intensities indicate that hematite is the only iron mineral in the Lie segang rock, i.e., no hydrous iron oxides are present. This observation was also confirmed by examinations of water content and infrared spectroscopy.