The Fe/Ni distributions between octahedral and tetrahedral sites in pentlandite (Fe_4.40Ni_4.57Co_0.03S₈) from a Sudbury Ni ore deposit were determined at 300K, at 533K, and again at 300K after heating with an X-ray single crystal method using the anomalous dispersion effect. X-ray intensities were measured with monochromatized synchrotron radiation (λ=1.7565 Å). The Fe/(Fe+Ni) ratios in the octahedral sites are 0.69(5), 0.29(6) and 0.29(6) at 300K, 533K and 300K after heating, respectively. The corresponding cell dimensions are 10.051(1), 10.211(3) and 10.109(3) Å. Using the Fe/Ni distributions and cell dimensions determined in this study, the dependence of the Fe/Ni distribution on pressure (Pa) and temperature (K) were estimated as lnK=−3.33+1.28×10³T⁻¹+8.17×10⁻⁷PT⁻¹, where K=(Fe/Ni)_octahedral/(Fe/Ni)_tetrahedral.

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The crystal structures of seventeen natural Mg–Fe olivines from nine rock specimens of seven different rock types were refined by X-ray diffraction method. Intensity data of the two olivines were also obtained at high temperatures ranging from 200°C to 700°C. The site occupancy refinements of the unheated olivines showed that volcanic olivines and a metamorphic olivine have a slight preference of Fe for the M1 and M2 sites, respectively. In-situ high temperature X-ray experiments showed that the K_D (= Fe/Mg)_M1/(Fe/Mg)_M2 values of the heated olivines increased with increasing temperature, and the K_D values of the olivines heated above 600°C increase with increasing fayalite content.

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The mineralogical properties and rehydration behaviors for Na-rectorite from Makurazaki, Kagoshima Prefecture, Japan were examined.
X-ray diffraction analysis showed that the mineral has 25.3Å average basal spacing, which moved to 26.8Å by treatment with ethylene glycol. Chemical analysis proved a structural formula of (Na_0.81K_0.40Mg_0.07Ca_0.05) (Al_3.66Fe³⁺ _0.18Mg_0.06Ti_0.07) (Si_6.64Al_1.36)O₂₀(OH)₄, and the compositions of mica and smectite layers belong to those of paragonite and beidellite, respectively.
Ca-, Mg-, Na- and K-saturated specimens showed remarkable rehydration properties after heating at various temperatures. The d(001) spacings of the specimens heated below 400°C did not change on rehydration. After rehydration of the specimens heated above 500°C, the Ca- and Mg-saturated specimens showed contraction of the d(001) spacings, and the Na- and K-saturated specimens showed expansion of the d(001) spacings. In the case of exposure to air for the specimens heated at 400°C, the K-saturated specimen showed strong rehydration properties, while the Mg-saturated specimen did not rehydrate even after exposure to air for 2 days. These rehydration behaviors for the specimens heated below 400°C can be explained by rehydration mechanism for smectite group minerals. However, the rehydration behaviors of the specimens heated above 500°C are completely different from those of smectite group minerals. These behaviors are due to difference of positions of the interlayer cations after rehydration. In the case of specimens heated below 400°C, the interlayer cations migrated into hexagonal holes and returned to the interlayer space after rehydration. In the case of specimens heated above 500°C, on the other hand, the interlayer cations were fixed to the hexagonal holes, and keeping this rearranged configuration, water molecules were regained in the interlayer space. Therefore, the coordination states of water molecules to the interlayer cations changed. DTA and IR spectra for rehydrated specimens supported this consideration.

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The electron-density distribution in a crystal of LiTaO₃ has been investigated with the single-crystal X-ray diffraction method. The crystal has the cell dimensions a=5.15329(7) and c=13.7806(5) Å with the space group R3c and Z=6. Residual electron densities due to anharmonic thermal vibration were observed around the Ta⁵⁺ ion. Refinement with anharmonic thermal parameters improved the coincidence of the observed and calculated structure factors significantly. The C₃₃₃ (the coefficient of Δz³) value of Ta⁵⁺ is most significant among the third and fourth order anharmonic potential parameters. It has revealed that significant errors are sometimes introduced into positional parameters if contributions of odd order terms of anharmonic potentials are ignored.

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A single crystal of ZnSiO₃ in the monoclinic pyroxene structure was investigated under pressure up to 139 kbar using a diamond-anvil, high-pressure cell and four-circle X-ray diffractometer. The discontinuous change of compressibility and optical property were found at 19 kbar and 51 kbar, suggesting possible phase transitions.

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