Coexisting amphiboles in samples from three manganese ore deposits in Japan have been investigated by an electron probe microanalysis and an X-ray powder diffraction method. The coexistences of manganoan actinolite and tirodite (from the Fukadaniguchi mine and the Fukumaki mine), actinolitic hornblende and tschermakitic hornblende (from the Fukumaki mine), manganoan ferri-winchite, manganoan magnesio-riebeckite, and manganoan actinolite (from the Nodatamagawa mine) are newlydescribed. Assemblages of amphiboles from manganese ore deposits in Japan, were classified according to their occurrences and their associated minerals.

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The original samarskite structure was recovered by annealing metamict samples for 3 hours both in air at 720°C and in a reducing atmosphere (H₂) at 680°C. Lattice parameters of the annealed samarskite in air are a=5.66(1)Å, b=4.910(6)Å, c=5.19(1)Å, β=90.4(2)°, and they are in good agreement with those of the annealed samarskite in the reducing atmosphere and previous data. The samples annealed at 1200°C in air resulted in the formation of four stoichiometric phases ; fergusonite, pyrochlore, FeNbO₄ and U₃O₈·1.5 Nb₂O₅. The samples annealed at 1080°C in a reducing atmosphere for 162 hours resulted in the formation of two stoichiometric phases; fergusonite and tapiolite. Products obtained by annealing were found to be distinctly dependent on annealing conditions (Redox, temperature, time). Some of the diffraction patterns for the products were in good agreement with previous data. DTA and Mössbauer spectra for samarskite are also presented.

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Computational techniques to simulate crystal structures of minerals under external forces are described. The method is based on minimizing the calculated energy of the entire system with respect to the structural variables. Illustrations of the technique are given by its application to the calculations of the structural and elastic properties of α-, β- and γ-Mg₂SiO₄. The potential energy of our model includes Coulomb and repulsive interactions between nonbonded atoms, as well as bond-distance-stretching energy terms for Si-O distances and bond-angle-bending energies for O-Si-O angles.

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