Mineralogical properties of the green-colored material filling amygdales of the basalt at Kokuzô, Maruko-machi, Nagano Prefecture has been studied in detail. The chemical composition and X-ray powder data of the untreated sample resemble those of vermiculite. But, referring to other Xray data obtained after heating or treatment with ammonium nitrate or ethylene glycol, it has been revealed that the green material is a very complex mixture of clay minerals, namely, montmorillonite, vermiculite, random interstified combination of chlorite-vermiculite, and also regular interstratified combination of montmorillonte-vermiculite.

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Tertiary iron sand beds, 1 to 2mm thick, occur intercalated within tuff or tuffaceous sediments in Niiharu-mura, Tone-gun, Gumma Prefecture. It is worthy of notice that clear prismatic crystals of zircon (0.1-0.5mm) and fragments of allanite crystal (0.1-0.5mm) are contained in the sand beds. Sand grains are cemented by green clay material, which is largely composed of extremely fine particles accompanied by fibrous flakes, showing mean refractive indices of 1.62-1.63 and strong pleochroism (bluish green to pale yellow). The green material has the following chemical composition: SiO₂ 34.95, % Al₂O₃ 22.34, Fe₂O₃ 6.95, FeO 16.09, TiO₂ 0.99, MnO 0.13, CaO 1.54, MgO 1.31, Na₂O 0.45, K₂O 1.85, H²O (-) 5.92, H²O (+) 7.77, total 100.29%. X-ray investigation suggests that the material is composed of very complex mixture of clay minerals:(1) chlorite (probably an iron-rich sort), having structure composed of an interstratified combination of 7Å and 14Å layers;(2) hydrous complex of mica clay minerals (probably iron-rich sorts). Chemical characteristics of each mineral were not determined in detail because of dfficulty in separating them.

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Magnesium-rich clays are distributed around the hydrothermal replacement deposit of gypsum in the Tertairy rocks of the Iwami mine, Shimane Prefecture. Generally speaking, the principal constetuent mineral is a magnesium-rich chlorite, accompanied by other accessory minerals such as montmorillonite, illite, 11 Å mineral, 30 Å mineral, gypsum, quartz, calcite, and pyrite. In the light of X-ray data, the 30 Å mineral can be identified as interstratified mineral of chlorite-montmorillonite, and 11 Å mineral is hydrous complex of mica clay mineral; intex stratified combination of illite and its more hdrated layers. Particularly some specimens have very complicated mineral compositions containing 30 Å mineral, chlorite, and montmorillonite Chemical compositions and differential thermal analysis curves are shown.

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