The crystal structures of one high-symmetry (P4⁄nnc) vesuvianite from Japan and three low-symmetry (non-P4⁄nnc) vesuvianites from Japan, Pakistan and Norway were determined by single-crystal X-ray diffraction method. The four crystals have the following cell parameters; a=15.568(2), 15.564(2), 15.559(3), 15.572(2); c=11.790(1), 11.841(1), 11.826(2), 11.833(2) Å, respectively. The structure refinements were carried out in the space group P4⁄nnc, P4⁄n, P4⁄n and P4nc, respectively. The final R indices for 1821, 3024, 3743 and 2053 independent reflections are 0.038, 0.063, 0.082 and 0.038, respectively.
The chemical analyses of low-symmetry vesuvianites indicate a very small amount of F and almost negligible Cl while high-symmetry one contains a considerable amount of F and Cl. The high-symmetry vesuvianite can contain Cl⁻ ions preferentially occupying the O(10) site which is split into two sites; one is occupied by Cl⁻ and the other by F⁻.
The ordering of cation and vacancy in the two alternately and statistically occupied sites in a unit cell causes the lowering of the symmetry from the space group P4⁄nnc to P4⁄n or P4nc. The ordering scheme of P4nc structure is first confirmed. In the three low-symmetry vesuvianites, the refined site occupancy ratios for occupied (B(a) and C(a)) and vacant (B(b) and C(b)) sites are 63:37, 62:38 and 92:8(%), respectively, and the values suggest the ordering in these crystals is not complete.
In low-symmetry vesuvianite, the satisfaction of the local charge balance on O(10) anions requires alternate occupancy of oxygen and hydroxyl with an associated hydrogen bond and ordering sequences of cations. In Cl- and F-bearing high-symmetry vesuvianite, on the other hand, occupying of Cl and F in O(10) sites interrupts the sequences of cations and vacancies along the fourfold rotation axes.

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Crednerite from the Gozaisho mine occurs as black tablets in close association with Sr-bearing barite in a coarse-grained rhodonite ore with minor quartz, braunite, spessartine, aegirine, and ganophyllite, rarely with långbanite as a product of regional metamorphism. The microprobe analysis gives Cu₂O 47.25, Mn₂O₃ 41.78, Fe₂O₃ 10.34, total 99.37%, corresponding to Cu_1.00(Mn_0.80Fe_0.20)_Σ1.00O₂ on the basis of O=2, or ferrian crednerite. The X-ray powder pattern is indexed on a monoclinic cell with a=5.552Å, b=2.894Å, c=5.899Å, β=104.29°, Z=2. The valence loaded ideal formula is Cu¹⁺Mn³⁺O₂. The mineral is not of secondary but primary formation as a metamorphic mineral under the oxidizing condition, which had annihilated Fe²⁺ and influenced the chemical compositions of the associated rhodonite and ganophyllite both devoid of FeO despite their capabilities to involve Fe²⁺. Also, the metamorphic condition enabled the formation of solid solution containing 20 mole% of CuFeO₂, but this was not attained under the superficial oxidizing condition under which all the known crednerites have been formed.

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The structural analysis of ground kaolinite and pyrophyllite prepared by dry grinding with the different periods has been made by determining the radial distribution functions from X-ray diffraction data. The SiO₄ tetrahedra remain unchanged in either sample of ground kaolinite and pyrophyllite. Whereas, the increment of grinding time has been found to induce the decrease of oxygen coordination number and the corresponding interatomic distance around aluminum.

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Solid solutions in the system Al₂(SO₄)₃ [millosevichite] – Fe₂(SO₄)₃, were synthesized by heating various mixtures of anhydrous end members at 600°C for 2 weeks under 1 K bar with a hydrothermal apparatus. Run products were checked by X-ray powder diffraction and the complete solid solution between two end members were confirmed. They are rhombohedral with space group R-3. Parameters of the hexagonal unit cell and refractive indices are a=8.027Å, c=21.36Å, n=1.545 for Al end member and a=8.232Å, c=22.17Å, n=1.775 for Fe end member. They increase linearly by the substitution of Fe for Al.

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