Three natural cristobalite specimens from different localities in Japan were prepared by treating the raw specimens with fluoboric acid. The sample obtained from “Beppu Hakudo” gave rather sharp X-ray powder patterns in which many of the lines in the region of back reflection which had first been described in the writer's previous paper were recognized again. The lattice constants of the sample are larger than those of the standard artificial cristobalite by 0.30%. this discrepancy is attributable to the simultaneous crystallization of a small amount of tridymite in the sample. The patterns of the other two natural specimens are rather obscure, but their spacings are in agreement with the standard values within the experimental errors.

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The mode of occurrence of metacinnabar at the Gading mine, Sarawak, is described. It was identified by X-ray powder patterns which were in good accord with those of artificial metacinnabar. Occurrences of the mineral in Japan are summarized, and among them the oolitic texture and metacinnabar veinlet in the ore of the Nikô mine are noticeable. Although some pseudomorphs of cinnabar after metacinnabar have been described from japan, the two minerals, in general, seem to have been precipitated independently from hydrothermal solutions.

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Dielectric dispersion of natural smoky quartz was observed in the audio-frequency region at about 400°C. The enthalpy of activation for the dielectric relaxation was about 50 kcal/mole in contrast with a value of about 20 kcal/mole for natural colourless quartz. By thermal bleaching, the enthalpy of activation falls to the value for natural colourless quartz.
Exposed to X-rays, the bleached quartz coloured again and the value of activation enthalpy recovered, and to γ-rays of about 10⁵ to 10⁷r. in total dose, Coloration also attained, but the effect was different from that by X-rays. A linear relation was found between the energies of activation and the logarithms of the total doses of irradiation.
Probable molecular mechanisms responsible to these dielectric phenomena were proposed. The rôle of water molecules trapped in the structure was discussed.

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The manganese ore, locally called “Kimiman” or “Kibiman” by the miners at the Noda-Tamagawa mine, is composed essentially of pyrochroite ?? Mn(OH)₂ ?? hitherto known as a rare mineral. More than 50, 000 tons of the pyrochroite ore have been shipped from this mine for metallurgical uses since 1950. The ore consists mainly of fibrous pyrochroite pseudomorph after manganosite with small amounts of manganosite, galaxite, tephroite, rhodochrosite, barite and alabandite. The pyrochroite occurs in scaly aggregates. When fresh, it is white but when exposed in air its colour changes into brown to black. Extinction is parallel to the elongated fiber. Character of zone is positive, ε=1.683, ω=1.725 and ω-ε=0.042. The unit cell dimensions obtained from the powder data: a₀=3.323Å. and c₀=4.738Å. The pyrochroite ore is considered to be hydrothermal alteration product from the manganosite ore, which may have been formed as dissociation product from the rhodochrosite ore of sedimentary type during the period of contact metamorphism of granitic intrusion.

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