The limonite ores from the Horaitakamatsu Mine may be classified into three types according to their external appearance and mineral compositions as follows:
(1) Dark brown compact ores, composed of goethite only.
(2) Light reddish clayey ores, characterized by the presence of hematite and the intricated mineral contents, namely, montmorillonite, α-cristobalite, quartz, tridymite, goethite and hematite.
This complication is ascribed to the fact that the clay altered from volcanic ash mingles in this ores.
(3) Dark yellow clayey ores, composed of goethite and quartz.
A limonitic substance replacing a kind of moss is found in this mine, and from the results of its investigations, it is ascertained that it is not hydrous ferric oxide but basic ferric sulphate. The results were reported in another paper.