The thermal dehydration behaviours and x-ray diffraction features of heated kaolinite and halloysite have been investigated, especially for the so-called metakaolin state.
The results on the thermal dehydration studies show that the dehydroxylization of well-crystallized kaolinite is likely to take place with two steps, the first of which starts at about 520°C. Approximately one fourth of hydroxyl groups are expelled gradually between 650°C and 950°C. This is the second step of dehydroxylization. A crystalline-like structure is proposed for the first step of dehydroxylization.
It is also pointed out that the hydroxyl groups of halloysite are easily expelled, but the recombination of the destroyed structure to a new phase needs much more energy than in the case of kaolinite.

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The biotite crystals described in this paper are found as an ingredient mineral of hornblende biotite granite exposed on Myogo-ho, Kawasaki-machi, Shibata-gun, Miyagi Prefecture. They are also contained abundantly in the sand derived from the weathered rock. These crystals occur as six-sided short prisms or plates. Hardness: 2.5-3. Colour: brownish black with brownish streak. Indices of refraction: α=1.620-1.621, β=1.658, γ=1.658-1.659. Further, they are characterized by the small optic angle ?? (-)2V ?? 0° ?? and weak dispersion (υ>ρ). A chemical analysis gave the following result for this mineral: SiO₂ 33.92, TiO₂ 2.91, Al₂O₃ 13.88, Fe₂O₃ 3.39, FeO 26.66, MnO 1.35, MgO 4.86, CaO 0.75, K₂O 7.46, Na₂O 1.70, H₂O (+) 3.53, H₂O (-) 0.16, total 100.57%. Moreover, the X-ray powder diagram of this specimen agrees with that of biotite rich in ferrous iron on its octahedral layer.

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Zircon grains, isolated from the granite exposed at Kitashirakawa in the suburbs of Kyoto City, are separated under the binocular microscope into two main groups: the transparent grains and the cloudy ones covered with microfissures. Each zircon grain is fused into a NaF bead. The examination of the bead by fluorescent method reveals that the transparent group is much lower in uranium content than the other. The uranium behavior in the zircon grain is treated both petrologically and geologically.

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The crystal structure of orpiment, As₂S₃, was refined by the Fourier synthesis. The unit cell has the dimensions, a=11.46Å, b=9.57Å, c=4.22Å and β=90.5°, containing four As₂S₃. The space group is C⁵_2h-P^2₁/n. The structure is essentially the same as one described earlier.

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