There are two groups of rocks in the Kayanoki area, Amakusa County; the Cretaceous sediments of the Himenoura group, and rhyolite dikes of Miocene epoch. The Himenoura group consists principally of shale, sandstone, and conglomerate. The rhyolite dikes intruding the Himenoura group are partly or entirely altered and have been mined as potter's clays.
The potter's clays are composed of quartz, sericite, kaolinite, plagioclase (Ab₉₅-Ab₈₅), potassium feldspar, and accessory pyrite, siderite, calcite, and apatite. Fine-grained sericite is a mixture of 1M and 2M₁ polymorphs; coarse-grained muscovite is 2M₁ polymorph. The latter is found in the intensively altered rhyolite dikes.
The sedimentary rocks in contact with the altered rhyolite dikes contain more sericite and kaolinite than the other sedimentary rocks and are associated with the interstratified sericite-montmorillonite and chlorite-expandable layer.

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Xenoliths in the Kitomyo ultrabasic body (NS-2.5km, EW-4.5km in width) in Kizawa village, Tokushima Prefecture, are composed of mainly amphibolites, psammitic and basic schists with albite spot, quartzose schists, greenstones and sedimentary rocks, the latter two being derived from country rocks. The mode of occurrence, petrographic features and chemical analyses of garnet, chlorite and amphiboles of the metamorphic rocks are described. Petrographically, the low grade schist xenoliths are quite similar to basic and psammitic schist of the Sanbagawa metamorphic belt, and they are distinct from the Terano metamorphic rocks. But the K-Ar ages of muscovites in psammitic and quartzose schist with albite spot are 402 m. y. and 405 m. y. respectively. The significance of the presence of Sanbagawa-type schists in the ultrabasic body of the Kurosegawa tectonic zone is briefly discussed.

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The join MgSiO₃-MgAl₂SiO₆ was studied with the special reference to the solubility of Al₂O₃ in enstatite, above 1300°C. MgAl₂SiO₆ is incorporated in enstatite as much as 3.5wt.% (1.75wt. % Al₂O₃) at atmospheric pressure. At subsolidus temperatures the phase assemblage protoenstatite_ss+forsterite was confirmed in the composition ranging from 96.5 to 94.5wt. % MgSiO₃. In the more aluminous region the subsolidus phase as-semblage is protoenstatite_ss+forsterite+cordierite_ss. The experimental result indicates that the composition of protoenstatite lies not only on the join MgSiO₃-MgAl₂SiO₆ but also has a solid solution area on the MgO-Al₂O₃-SiO₂ plane as shown in Fig. 4. The unit-cell dimensions of the protoenstatite_ss crystallized at 1300°C were determined. a, b, and V decrease with increasing Al₂O₃ contents in the protoenstatite_ss. The application of the results to meterorite as well as terrestrial rock is discussed. The Al₂O₃ contents of enstatite in meteorite may be used as an indicator of temperature scale.

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