The modes of occurrence, optical properties, X-ray diffraction data, physical properties, and chemical composition of arsenian hauchecornite from the Tsumo mine were described. The mine is one of the pyrometasomatic ore deposits in the Sangun metamorphic terrain, Southwestern Japan. The present hauchecornite is the first finding in Japan.
The mineral is found in bornite-chalcopyrite ore at Maruyama deposit of the Tsumo mine and associated intimately with bornite, chalcopyrite, and sphalerite, and accompanied by a mineral of linnaeite series, sometimes, with small amounts of native gold, tetradymite, stannoidite, mawsonite, native bismuth, and an unknown mineral of Cu–Ag–S system.
Grain size of the mineral is generally in the range from 0.05 to 0.7 mm across. Reflection colour is pinkish white with yellowish tint and a little lighter than that of pyrrhotite. Reflectance values are 40.0–44.6% (470 nm), 44.3–49.3 nm (546 nm), 46.2–51.1% (589 nm), 48.2–53.3% (650 nm). Microhardness value is 435–516 kg/mm².
The mineral is tetragonal, a₀=14.56±0.01Å, c₀=10.87±0.01Å, Z=8, cell volume 2295.2±3.0ų, calculated specific gravity 6.62 g/cm³. Chemical composition determined with the electron probe microanalyser is as follows: Ni 45.02, Fe 0.42, Co 0.57, Bi 26.43, As 4.19, Sb 0.46, Te 0.19, S 22.25, total 99.51 wt.%. Empirical formula is (Ni_8.80Fe_0.09Co_0.10)_Σ8.99(Bi_1.46As_0.64Sb_0.04Te_0.02)_Σ2.16S_8.00 on the basis of S=8.

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Crystals of KMg_2.75Si_3.5Al_0.5O₁₀F₂ were synthesized from a mixture of KF, MgF₂, MgO, Al₂O₃ and SiO₂. They have a structure of the 1M type mica with cell dimensions of a=5.292(1), b=9.164(5), c=10.143(1)Å and β=100.07(2)°. The structure was refined with the full-matrix least-squares procedure to the final R value of 0.029 for 1228 observed reflections. The observed distortion of the (Si, Al)O₄ tetrahedron is in good agreement with that predicted from the chemical formula of the crystal. The ditrigonal distortion of the tetrahedral sheet is intermediate between those of KMg_2.5Si₄O₁₀F₂ and KMg₃Si₃AlO₁₀F₂, having the tetrahedral rotation angle of 3.63°.

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Crystals of KMg₃Ge₃AlO₁₀F₂ were synthesized from a mixture of KF, MgF₂, MgO, Al₂O₃ and GeO₂ by heating at 133°C and subsequent slow cooling. They have a structure of the 1M type mica with cell dimensions of a=5.417(6), b=9.345(5), c=10.468(1)Å and β=100.03(3)°. The structure was refined with the full-matrix least-squares procedure to the final R value of 0.037 for 1365 observed reflections. The (Ge, Al)–O_apical distance is 1.741 Å and the mean (Ge, Al)–O_basal distance is 1.744Å. Both of M(1)O₄F₂ and M(2)O₄F₂ octahedra are considerably flattened, having the octahedral flattening angle of 60.2°. The ditrigonal distortion of the tetrahedral sheet is much larger than that of the corresponding aluminosilicate mica, giving the tetrahedral rotation angle of 15.9°.

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Monoclinic tridymite was found in volcanic rocks from three localities; Yugawara, Harius and Mt. Myoho in Japan. The unit cell parameters of the Yugawara tridymite are a=25.89, b=5.00, c=18.59Å and β=117.7°, and space group is Aa or A2⁄a. This monoclinic tridymite was transformed to the form with n=10 by rapid cooling from high temperature.

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Brookite was obtained from fresh coprecipitates prepared by neutralization of TiCl₄ and CaCl₂ solutions, under hydrothermal conditions of 220–560°C and water pressure of 1 kbar. This phase developed from anatase and through the decomposition of a titanate in solutions containing Ca⁺⁺ ions, which were established as a new stabilizer for the formation of the phase. A reaction diagram, indicating the formation region of the phase, was determined.

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