On the wall of a tunnel dug in sandy tuff of Fukuda formation of Neogene system southwest of Yoshimi hill in Yoshimi Town, Hiki County of Saitama Prefecture, sulfate minerals have crystallied on the surface due to weathering of rocks. Amount of crystallization changes considerably between dry and wet periods, and distribution and mineral species also vary. Minerals confirmed with results of XRD as surface crystals are mostly alunogen, jarosite and gypsum, accompanied with halotrichite, epsomite, thenardite, tamarugite, and sodium alum as well. Crystallization of these minerals, particularly of alunogen, on the weathering process of rocks indicates that this weathering is advancing in strongly acidic environment compared with that of ordinary weathering. Alunogen is a mineral that is originally formed in concern with water vaporization in a strongly acidic environment as a secondary mineral mainly of volcanic sublimate, sinter and sulfide deposit. At this site of study, alunogen crystallizes at ordinary temperature by covering rack surface in skinny shell, and in paragenesis with jarosite. It is regarded by observing formation process of the crystallization and its distribution that alunogen crystallized with action of water strongly acidified by the formation of jarosite and oxidation of pyrite and H₂S.

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Crystal growth mechanism for hydroxyapatite under pseudophysiological conditions was investigated using hydrothermally synthesized single crystal as a seed. In situ surface observation and measurements of step velocity indicated that the rate determining process of the growth was incorporation of the growth unit into the crystal lattice. Step kinetic coefficient on (1010) face was the order of 10^-4 cm/s, which was 2-3 orders smaller than that for soluble inorganic crystals and the same order as that for macromoiecular protein and virus crystals. The edge free energy of nucleated island on (0001) face, which was estimated using phase shift interferometry, also showed a same order as that for protein crystal. These results strongly suggest that a growth unit of hydroxyapatite was a form of cluster and not ionic species. This hypothesis was confirmed by dynamic light scattering measurement of the particle size in the solution in which hydroxyapatite grew. Around 0.8 nm in diameter of calcium phosphate clusters were detected by light scattering measurement. In the crystal structure of hydroxyapatite, two kinds of Ca₉(PO₄)₆ chiral clusters called C0 and C50, both of which are about O.8 nm in diameter, can be defined. A growth model based on the stacking of these chiral clusters was presented. Hydroxyapatite can grow only by two kinds of stacking. One is stacking of either C0 or C50 clusters forming a primitive lattice with two-dimensional hexagonal packing. The other is stacking of C0 and C50 alternatively with hexagonal closed packing.

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Advantages of mineralogical approach in searching new inorganic materials are introduced. Recent developments of synthesis and analysis methods in mineralogy are overviewed. Searchs for new inorganic materials such as new cluster compound Y₂C₂I₂ and lithium-intercalated compound HfNCl are reviewed. The application of recently innovated techniques to the characterization of materials under extreme conditions is necessary to understand the earth's deep interior; such as thermal and elecrical conductivity mechanism in lower mantle. Recent advances in science and technology for new inorganic materials should be linked to those in mineralogy and vice versa.

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It is introduced that usefulness of mechanical spectroscopy in searching many kinds of ceramics under extremely high temperatures. The data from the mechanical spectroscopy can help to understand the grain boundary sliding mechanism due to oxygen diffusion in glassy film. Inelastic mechanism at the grain boundary controls the internal friction background and creep. We showed experimentally that oxygen diffusion mechanism in zirconia ceramics causes an internal friction which is associated with stress relaxation due to stress induced motion of oxygen-dopant pair.

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Thermal diffusivity measurements of silicate melts at high temperature have systematically been made by applying the differential three layered laser flash method. Data processing has also been developed in order to separate the contribution due to radiative component from measured values at high temperature by considering the variation of the absorption coefficients when adding TiO₂ ZrO₂ or iron oxide. The ability of thermal diffusivity measurement system for micro region of composite based on the thermoreflectance method is also demonstrated by using the result of NbTi/Cu composite.

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A variety of interesting modulated structures are frequently observed in composite crystals with plural subsystems, because there are mutual lattice modulations between them. By considering superspace group symmetry for quasiperiodic systems, atomic modulation functions can be applied to the structure refinement of the modulated composite crystal. By the superspace group approach, we can also understand structural interactions between substructures. A modulated structure analysis of the composite crystal with layered substructures using (3+1)-dimensional superspace groups is introduced as an example.

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Recent studies on the high-temperature martencitic phase transition of cuspidine-type rare-earth aluminates (RE₄Al₂O₉, RE: rare-earth elements) were reviewed. Calorimetry, dilatometry, thermal gravimetry and crystal structure analyses of RE₄Al₂O₉(RE=Y) revealed a reversible phase transformation at around 1370°C with thermal hysteresis. The cell volume of the high-temperature phase is approximately 0.4% smaller than that of the low-temperature phase. The high-tempera-ture phase crystallizes in a monoclinic cell, a space group P 2₁/c. This is identical to the space group of the low temperature phase. Phase transition temperatures of cuspidine-type rare-earth aluminates (RE₄Al₂O₉, RE=Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) and gallates (RE₄Ga₂O₉, RE=La, Pr, Nd, Sm, Eu, Gd) decreased from 1300°C (Yb) to 1044°C (Sm) for the aluminates and 1417°C (Gd) to 1271°C (La) for the gallates with increasing ionic radius of the rare-earth elements.

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Mmolecular simulation methods are reviwed as a major component of the design and evaluation system for inorganic materials. The molecular simulation system is the method to analyze and predict macroscopic properties from the behaviour of motions and arrangement of atoms and molecules. The method involves molecular dynamics and Metropolis Monte Carlo methos, and from empirical to first principles approach. In the emprical approach, molecular simulation methods can be applied to mesoscopic phenomena and polycrystalline materials. Some examples of the applications to zeolite-gas molecules systems and solid electrolites, and also to macro properties of complex materials are introduced.

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