Ways of manufacturing silica glass blanks with a homogeneous refractive index (n) distribution by appropriately distributing the OH-group and Cl were discussed. First, the effect of fictive temperature, which was considered to be set in the cooling process of stress relief annealing, was estimated. Then, the effects of OH-group and Cl were examined in terms of the distribution profiles of the relative n for silica glasses without other impurities. The literature formulas for the effects of OH-group and Cl on n, Δn_OH=−1×10⁻⁷⁄OH (mass ppm) and Δn_Cl=−1×10⁻⁷⁄Cl (mass ppm), were shown to be reasonable.
Calculations show that there were three patterns, in which the concentration of OH-group and Cl were distributed in the ingot so as to offset the effect of the fictive temperature, for manufacturing silica glass blanks with homogeneous n distribution.

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Celestine from the Asaka gypsum mine, Fukushima Prefecture, was found as aggregates of grains on one side of flattened and elongated aggregates composed of subparallel arrangement of fibrous gypsum collected in the dump. This association is considered to be a hydration product of strontian anhydrite (SrO up to 0.94 wt.%) also found in the dump. The hydration process involved the preferential conversion of the CaSO₄ molecule in the anhydrite into gypsum, but the SrSO₄ molecule remained intact and eventually crystallized as celestine. The formation of such celestine was favoured by the absence of any hydrated strontium sulphate and the nature of gypsum excluding the substitution of strontium for calcium therein under the condition where such a hydration process took place.

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Local structures around transition-metal atoms were investigated on glasses in the systems CaMgSi₂O₆–CaFeAlSiO₆ and CaMgSi₂O₆–CaCrAlSiO₆ with the X-ray diffraction technique. The correlation functions of the glasses in the former system indicated that a part of Fe atoms have coordinations lower than sixfold. Since the melting points of the substances rise rapidly with the increasing amount of CaCrAlSiO₆, the glasses with CaCrAlSiO₆ contents up to 5 wt% were examined in the latter system. Within this compositional range, the correlation functions showed that Cr atoms have sixfold coordinations. The difference in the preference to the sixfold coordination between Fe³⁺ and Cr³⁺ ions is supposed to be due to the difference in the crystal-field stabilization energy.

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The subsolidus phase relations in the system MnFe₂O₄–Mn₃O₄ were established at temperatures between 450°C and 960°C under the oxygen partial pressures controlled by a hematite-magnetite buffer. The existence of two partial solid solutions of the end-members, a cubic phase of MnFe₂O₄ and a tetragonal phase of Mn₃O₄, were confirmed at the temperatures. The value of x in Mn_xFe_3−xO₄ of the cubic and the tetragonal phases was determined by a microprobe analysis. The two-phase region composed of these phases becomes wider with decreasing temperature as expected from the previous works. The influence of oxygen partial pressure on cation distributions in the tetragonal phase was calculated by the thermodynamic approach. The result indicates that the phases formed in the present experiment are in the true binary system.

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The crystal structure of Ba₄In₆O₁₃ was determined by the single-crystal X-ray diffraction method using a single crystal grown by the floating zone method. Ba₄In₆O₁₃ is isostructural with Sr₄Fe₆O₁₃ and crystallizes in the noncentrosymmetric space group Iba2 with the unit cell parameters a= 11.460(6) b= 20.95(3) c= 5.944(2) Å. The structure is classified as one of the perovskite-derivatives consisted of Ba₂In₂O₆- and Ba₂In₄O₇-slabs arranged perpendicular to the b-axis. The In(3)-polyhedron in the perovskite-type Ba₂In₂O₆-slab is a distorted octahedron, whereas In(1)- and In(2)-polyhedra in the Ba₂In₄0₇-slab are described as strongly distorted square pyramids. Each polyhedron of In(1) and In(2) shares edges with each other. The sharing scheme of the In(1) polyhedra is similar to the cases for V atoms in CaV₃O₇ and CaV₄O₉, whereas that of the In(2) polyhedra is uncommon.

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