Paigeite from Kamaishi, Iwate Prefecture, with a composition near to the Fe end-member of ludwigite group, has been described. The mineral, a product of boron metasomatism related with a granodioritic intrusion, is found as fibrous aggregates associated with magnetite, hedenbergite, andradite, phlogopite, pyrrhotite and chalcopyrite in the iron ores of the skarn type. Its X-ray diffraction pattern is very similar to those of minerals of the ludwigite group. Oremicroscopic observations have been made. Chemical analysis gave the following percentages and formula: SiO₂ 1.16, TiO₂ 0.11, Fe₂O₃ 29.84, FeO 48.72, MnO 0.62, MgO 1.51, CaO 1.60, Na₂O 0.29, B₂O₃ 13.24, CO₂ 1.14, H₂O(+) 0.70, H₂O(-) 0.52, S 0.09, Total 99.54; (Fe″, Mg, Mn″) ₂Fe′′′BO₅.

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Clinoclasite, a basic arsenate of copper, from the Kitabira mine, Yamaguchi Prefecture has been described. It is found usually as massive aggregates of small flakes with limonite or iron-rich clay. The crystal is platy parallel to (001), and has monoclinic symmetry. The cell dimensions are a₀=12.48Å, b₀=6.48Å, c₀=7.27Å and β=99°02′ (morphologically). Forms: c(001), a(100), m(110), n(810), v( ?? 121) and s( ?? 552). Colour: greenish blue or deep blue. Streak: bluish green. Translucent. Hardness 2.5-3. Cleavage (001) perfect. Sp. gravity 4.33 (9°C). Opt. properties: α=1.739, β=1.87, γ ?? 1.9, 2V ?? (-) 50°:v⟩r strong; a ?? Z (c∧X ?? 10°); Pleochroic. Chemical analysis follows, As₂O₅ 29.66, Al₂O₃ 0.63, Fe₂O₃ 0.32, CaO 0.05, CuO 62.42, H₂O(+) 7.55, H₂O(-) 0.36, total 100.99%. The X-ray powder diagram of this specimen agrees well with the data given by Palache and Berry.

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The thermo-electric potentials of the pyrite from the Tutiya Isizaki mine, Hokkaidô, Japan were determined. The data obtained showed considerable variations. X-ray diffraction, microscopic, chemical and spectrographic studies were performed to ascertain the controling factor of the variation.
The results indicated that the effect of structural irregularities should be noted in particular among several factors causing the variation of thermoelectric properties of pyrite.

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The diadochic substitution of elements in the structure of silicate minerals is primarily controlled by the potential energies arising from the linkage of vicarious cations with an oxygen anion. A quantity, the index of diadochy, is proposed as a measure for the contribution of a cation to the potential energy, and is calculated for a number of elements of geological significance. The indices of diadochy of the elements harmonize generally with the natural geochemical behavior of the elements. Furthermore, possible effects of controlling factors other than the index of diadochy on the substitution are considered.

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