The formation process of dust grains around cool stars and the dust processing in the interstellar space are reviewed. Infrared spectral characteristics of circumstellar dust grains indicate that newly-formed grains are not in a highly crystalline state, but they are rather amorphous material. The dust formation process in circumstellar regions must involve kinematic aspects to a large degree. On the other hand, theoretical investigations suggest that the destruction process of dust grains in the interstellar space is quite rapid compared to the supply rate from stellar sources. Therefore, a large fraction of dust grains must be forming also in the interstellar space. Very few investigations have been attemped on the formation of solid particles under the interstellar harsh conditions, but they will be essential in the study of interstellar dust.

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This article discusses chemical composition and origin of solids including refractories, ices, and organics in the solar system and interstellar clouds as viewed from the condensation theory, and examines effectiveness and limitation of the equilibrium condensation theory. It is pointed out that, by taking cometary volatiles as a typical cosmic volatiles, the equilibrium condensation theory cannot be applied to low temperature condensation. Theories on the origin of cometary volatiles are discussed, and an observational clue to testing the theories is pointed out. Brief discussion is given on the advantage for formation of organic matter from volatile solids.

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The carbonaceous chondrites are the most primitive surviving materials from the early solar system, and thus they may provide important information regarding the early processes in the solar system. Some carbonaceous chondrites, CI and CM types in particular, consist in large part of fine-grained phyllosilicates, which account for most of the water in the meteorites (5-20 wt.% H₂0). Previous studies suggested that the phyllosilicates were formed by aqueous alteration on the meteorite parent body, but formation by direct condensation from the solar nebula has not been ruled out. This paper reviews, in the first part, results of mineralogical and chemical studies indicating the primitive nature of the carbonaceous chondrites, and reviews, in the second part, studies dealing with aqueous alteration experienced by these meteorites. This paper also discusses important points of information and their implications regarding the carbonaceous chondrite parent body.

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During the formation stage of the Earth, release of gravitational energy results in global melting and formation of a magma ocean. Thermal and chemical evolution of the magma ocean is examined based on a one-dimensional two phase flow model. The following results are obtained. When a magma ocean is vigorously convecting, chemical differentiation occurrs at the intermediate melt fraction (20-30%) because of large viscosity change. The magma ocean is kept just at the melt fraction, at which the differentiation proceeds most rapidly. Hence, chemical differentiation in the magma ocean seems to be inevitable, if density and composition difference exist between solid and melt. Chemical differentiation is controlled by composition difference of melt and solid phases at intermediate melt fraction rather than those at liquidus or solidus. Moreover, the resulted elemental distribution does not always reflect difference of partition coefficients.

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The phase transitions in the peridotite composition can account for the observed density and seismic wave velocity profiles of the upper mantle and the transiton zone. On the other hand, the lower mantle is not well constrained by the present experimental data, because of large uncertainties in the physical properties of the lower mantle minerals, and the temperature distribution in the lower mantle. Both a homogeneous mantle with a peridotite composition, and a stratified mantle with a peridotite upper mantle and a silica rich lower mantle can be consistent with the observed seismic data. The source upper mantle of the Al-depleted komatiite observed in the late Archean (2.5 Ga old) shows chondritic abundances of some key refractory lithophile elements compatible with the ultrahigh pressure minerals such as majorite and Mg-perovskite. The Al-depleted and Al-enriched komatiites generally observed in the early Archean (3.5-3.8 Ga old) show evidence of the majorite fractionation, melting at the depths of the transition zone. Recent Hf isotopic data of Al-depleted komatiites imply that the source mantle of the komatiites shows no evience of chemical layering in the early Archean; the source mantle of such komatiites was chondritic in terms of some refractory lithophile elements, such as Al, Ti, Sc, Hf, HREE. Solid state convection might have homogenized the stratification formed by global melting during the accretional stage of the Earth.

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Laboratory studies of physical properties of minerals and rocks can contribute to our understanding of dynamic processes of the Earth's interior through two different approaches. One is the study from the view point of the forward problem, that is to provide materials science data to predict dynamic processes of the Earth's interior. This includes the stduy of thermal expansion and rheological properties. The other is the study from the view point of the inverse problem. Materials science studies in this catagory include the studies on the relation of elastic properties and tectonic processes, such as the temperature sensitivity of elastic wave velocities and the changes of elastic wave velocities as a result of deformation. This paper reviews recent progress in these two areas and discusses some of the directions of future research in mineral and rock physics.

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Determining the source of mineral-forming elements in an ore deposit has proved difficult, since there are no unequivocal criteria for distinguishing “exogenic” ore minerals which are derived from the surficial reservoir where biogeochemical processes prevail from “endogenic” ones which are originated from the deep-seated reservoir (i.e. man-tle) through magmatic processes. The most commonly used criteria, those based on sulfur isotope data, have been often ambiguous: similar isotopic patterns can be generated by biological reactions and high temperature exchange reactions between sulfide and sulfate. Some insight into environmental controls on mineralization and processes of ore formation can be gained by studies of modern sedimentary environments. In this paper, I briefly review the known present-day sources of ore-forming elements, and attempt to assess the potential contribution of biologically-controlled sources to ore genesis, in the light of information obtained from some recent geochemical examinations of marine sediments and stratabound-type mineralizations.

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A mineralogical view of the earth's resources and environment is given by taking an example of the global geochemical cycle of uranium. The formation of U deposits is closely related to the evolution of the atmosphere, oceans, crust, microorganisms and plants. U is hence taken as a significant benchmark of the geohistory. The short-term geochemical cycle of U is considered to be mainly controled by the weathering of U deposits and the sink of U in marine sediments. This kind of short-term cycles of U and heavy metals are very important for the environmental problems such as the radioactive waste disposal. New methodologies such as microspectroscopic methods and the realistic geochemical kinetics should be developed in order to clarify mineralogical forms of unknown phases containing U and heavy metals and quantify the kinetics of their formation.

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