Cadmium contents of sphalerites are invariably higher than 0.9 wt% from both the vein-type and skarn-type major tungsten deposits at Kaneuchi, Ohtani, Takatori, Fujigatani, Kiwada, and Kuga mines. The contents are high compared with those of most natural sphalerites. Sphalerites from the quartz veins that intersect the skarns of the Fujigatani and Kiwada deposits are higher in cadmium contents than those from the skarns of the same deposits. Considering that tungsten mineralization in the Fujigatani and Kiwada deposits is closely related to the formation of quartz veins, it is likely that high cadmium contents of sphalerites have an intimate genetical relationship with tungsten mineralization in these deposits. Sphalerite from the quartz veins of the Suho ore body of the Kuga deposit is higher in cadmium content than that from the quartz veins of the Ideno-oku ore body of the same deposit. As the ore grade of tungsten in the Suho ore body seems to be higher than that in the Ideno-oku ore body, the higher cadmium content of sphalerite from the Suho ore body also supports the close relationship between cadmium content of sphalerite and tungsten mineralization.
Fluid inclusion data for the Kiwada and Kuga deposits suggest that the temperatures of the hydrothermal solutions do not significantly affect the cadmium contents of sphalerites from these deposits. It is suggested that high activity ratios of Cd²⁺/Zn²⁺ in the hydrothermal solutions are important as the cause of the enrichment of cadmium in sphalerite, and that these are characteristic for major tungsten deposits in Japan.

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Semi-emprical molecular orbital calculations (CNDO/2) have been performed for two large clusters with compositions of (Mg(1)₃Mg(2)₃O₂₂H₃₂)⁰⁺ and (Mg(1)₃ Mg(2)SiO₁₈H₂₄)⁰⁺ to evaluate the atomic charges on the Mg ions in enstatite. Hydrogen (H) atoms are attached to the outer oxygens in the clusters to keep charge neutrality. The two clusters are constructed to include all the polyhedra which share edges with the central Mg(1)O₆ and Mg(2)O₆ octahedra, respectively. The convergence in the energy minimization has been successfully achieved for each cluster. The estimated Mg charges are 0.73–0.75 and 0.69e for the Mg(1) and Mg(2) atoms, respectively. The charge on Mg(1) exhibits a value larger than that on Mg(2), which indicates that the M(1) site is more ionic than the M(2) site in orthopyroxene. This result is consistent with the previous investigations based on experimental charge analysis by accurate single-crystal X-ray diffraction, and on electrostatic site energy calculations.

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The electron-density distribution in a crystal of NiTiO₃ has been investigated by means of the single crystal X-ray diffraction method. A small amount of partial disorder was observed in the cation arrangement of the examined crystal. The difference electron-density maps showed an aspherical distribution of 3d electrons of the Ni²⁺ ion in the octahedral crystal field. Electron populations of the a, e(t_2g) and e(e_g) orbitals of Ni²⁺ were refined on the basis of the 3(C₃) crystal field, employing aspherical scattering factors for the cation. The refinement gave the populations 1.84(9), 4.00(10) and 2.16(7) for the respective orbitals. The Ti⁴⁺ ion lies in a negative region of the difference Fourier map after the spherical atom refinement, and a positive peak exists on the threefold axis at a position 0.49 Å apart from the Ti⁴⁺ ion towards the Ni²⁺ ion. These residual densities around Ti⁴⁺ are supposed to be caused by positive charge of the neighbouring Ni²⁺ ion. A residual peak is also observed at the middle of the neighbouring Ni²⁺ and Ti⁴⁺ along the threefold axis, which might be an indication of a metal-metal bonding. Refinements with anharmonic thermal parameters for the cations, up to the fourth order, revealed that anharmonicity is small at the room temperature in the present crystal.

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Corrensite occurs as alteration products in basic to intermediate volcanic and pyroclastic rocks. Chlorite and saponite also widely occur in the similar rocks. This paper proves that refractive indices and birefringence are effective for the discrimination among those minerals. Chlorite shows lower birefringence and higher refractive indices than corrensite. On the other hand, saponite shows higher interference color and low refractive indices. Corrensite has hybrid properties of the two end members forming the interstratification. Namely, birefringence of corrensite is in the range of 0.01 to 0.03 and it is lower than that of saponite and higher than that of chlorite.

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