Graphites in graphite schist of the Sanbagawa metamorphic belt, Tatarazawa, Fujioka, Gunma Prefecture, Japan, have been identified as ammonia-bearing graphite intercalation compounds (GIC). The ingestion of ammonia and sodium in GIC was confirmed by Nessler’s reagent, micro XRD (X-ray diffraction), EPMA (electron probe micro analysis) and micro Raman spectrometer.
The EPMA examination clarified that ammonia and sodium were inhomogeneously distributed in graphite grains. The Raman spectra revealed the natural GIC to be consistent with an ammonia-containing graphite. Occurrence of the specimens implied that genesis of natural GIC would have undergone ammonia-bearing hydrothermal process in the past.
A finding of graphite intercalation compounds proved that ammonia could be contained by graphite in Sanbagawa metamorphic belt. Likewise, a detection of sodium from graphite has an implication for the existence various graphite intercalation compounds awaiting discovery in such metamorphic rocks.

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The time-dependent loss of NaK_α X-ray intensity during the electron-probe micro analyzer (EPMA) analysis has become a serious problem in determining the chemical compositions of glass samples. An empirical method of correcting the Na-loss have been developed on the basis of observing decay curves of X-ray’s intensity and estimating the true Na intensities at 0s by EPMA.
However, the Na X-ray raw counts cannot be obtained from the monitor mode of our EPMA. In this study, we measured the time dependent decay profile by a line scan mode as a digital data without moving analytical spot for 20s with focused beam (5 μm analysis). Our method makes possible to evaluate the heterogeneity of Na concentration within a few μm scales and is suitable for the measurement such as vesicle-bearing and/or microlite rich samples. The corrected values by the present method are in good agreement with the chemical compositions determined by the defocused beam mode (30 μm analysis), which is not affected by Na-loss. Similar approaches to this method would be useful for the analysis of glass inclusion with narrow area.

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The theme of the 2003 symposium of the Joint meeting of the Mineralogical Society of Japan, the Japanese Association of Mineralogists, Petrologists and Economic Geologists, and the Society of Resource Geology is carbon and carbonate minerals. The minerals are important in many fields of earth sciences, material sciences, biological sciences, and environmental sciences. In the symposium, we chose seven invited papers for natural and synthetic diamonds, porous carbon materials, methane hydrates, rare-earth carbonate minerals, and paleoenvironmental studies using carbon and carbonate materials.

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Recent progresses on mineralogy and geochemistry of diamond and its inclusions are reviewed. There are two categories of materials contained in natural diamonds. One is chemical impurities such as nitrogen, boron, hydrogen, nickel, cobalt, etc. that are all structurally bound to the diamond lattice. The latter two transition metals are typical impurities in synthetic diamonds grown in metal solvent at high pressure and high temperature. Nitrogen atoms in natural diamonds are aggregated at elevated temperatures and for geological time. The aggregation state of nitrogen can be investigated with infrared spectroscopy and provide us with chronological information on the history of diamonds. The other category is mineral and fluid inclusions. Diamond is chemically stable and the hardest material, and inclusions in diamonds can bring versatile information of mantle. In particular, residual pressures recorded in the inclusions can provide us with depth information where their inclusions were entrained in host minerals. Furthermore, mineralogical and geochemical features of diamonds from the lower mantle recently found are reviewed.

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The diamond has highest properties amongst all the materials, such as elastic constant (hard-ness), thermal conductivity, transparency to optical wave and X-ray, wide bandgap semiconductor, and negative electron affinity, which lead to various kinds of applications in electronics industries. Heat sinks of laser diode for optical communication, surface acoustic wave devices for optical, wireless communication and oscillator applications have been already commercialized. The active devices such as high power transistors, electron emitters are the hopeful candidates for near future applications. The another applications such as tools, speaker diaphragms, optical windows, X-ray windows and sensors as well as electrode for electro-chemical applications are briefly introduced. According to the recent successful development of the technology of vapor phase growth, the large size diamond is ready to be provided with low manufacturing cost.

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Activated carbons and other types of porous carbons have been attracted many attentions in several industrial fields currently. However, experimental results for characterization of the structure of porous carbons show no distinct features, and accordingly the structural information obtained from the experimental results has been limited to qualitative one. This paper contains a quantitative characterization of porous carbons, especially for electric double layer capacitor applications. Investigations were carried out by applying new analysis methods to data by XRD measurement for microporous carbons, TEM observation of mesoporous carbons, and multilateral characterization of total pore and solid structures. It was also represented about a development of carbon-based electrodes for electric double-layer capacitors by using carbon aerogels known as one of the candidates for the application in this field. Some recent topics are addressed about a preparation of metal-loaded carbon aerogels by a pre-mixing method and an ion-exchange method, as well as their electric double-layer capacitor behavior estimated by cyclic voltammograms in 1M-H₂SO₄.

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Methane hydrate, called as “fiery ice”, is expected to be a fruitful natural resource, at the same time, methane is rather effective greenhouse gas than carbon dioxide. And, methane hydrate is thought to be the dominant constituent of the outer planets and their moons. Recent high-pressure studies on gas hydrate, including methane hydrate, have accumulated to give us a great deal of understanding of the structural changes in gas hydrates. A feature of structural changes in terms of pressure and guest size is summarised in the former part of this paper. The gas hydrate with the guest size from argon to methane finally take a common filled ice I_h structure, although they have different initial and intermediate structures. In the latter part, retention of the filled ice I_h structure of methane hydrate up to 42 GPa is described. In-situ x-ray diffractometry and optical observation revealed the existence of the filled ice structure with the volume change of 40% and large anisotropic compressibility. The meanings of the structural changes and the retention to very high pressure of methane hydrate on geological science and planetary science are also described.

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The carbonate ion with a triangle shape is always isolated from other carbonate ions in the crystal structure of a carbonate. The rare earth atoms in carbonate minerals tend to have higher coordination numbers in comparison with those in the silicates and phosphates, owing to the lower negative charge per an apical oxygen atom of the carbonate ion. The differences in coordination numbers and sizes of coordination polyhedra are observed between the smaller rare earth, e.g. Y, and larger rare earth, e.g. Ce, and the differences are directly reflected in the crystal structures of carbonates without infinite framework structures. The major part of rare earth carbonate minerals can be classified into four mineral groups, lanthanite, tengerite, bastnäsite and kozoite groups. The isomorphous substitution of rare earths with calcium can be observed in the kozoite group, as a solid solution series between kozoite-(Nd) and calcioancylite-(Nd), whereas non can be observed in the tengerite and bastnäsite groups. The bastnäsite group is unique to the other carbonate minerals because their crystal structures can accept both of the larger Ce and smaller Y ions.

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Sedimentary carbonate is the most successful material in paleoclimatological researches. Researches in this field are now challenging to extract high-resolution and quantitative records of millennial-century scales in order to predict the climatic changes due to global warming. The most promising study material is a reef coral, which records temperature (and salinity) changes in its annually-laminated aragonitic skeleton. Data from coral climatology and annually-laminated polar ice cores would contribute to climate prediction although the information is geographically limited in only tropical and polar areas.
For the information from temperate-subtropical climatic belts, carbonate paleoclimatology using speleothems is effective. Oxygen and carbon isotopic signatures of speleothems are now treated as possible proxies of water temperature and vegetation. Another promising material for the study on temperate-subtropical areas is a tufa, a calcitic deposit in freshwater environments of limestone areas. The tufa commonly shows annual laminations and advances to speleothems in its larger depositional rate (several millimeters per year) that allows higher analytical resolution. This study represents that rainfall events were recoded in a Japanese tufa deposit.

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The abnormally light carbon isotope compositions have been recognized in kerogenous and graphitic samples from the 2.7 to 2.1 Ga sedimentary rocks. Such light carbon isotope compositions suggest that methanotrophic micro-organism flourished in the contemporary oceans, also postulating methane accumulation in the stratified oceans. Periodic occurrence of the methanotrophic micro-organism is coincident with the periodicity of global volcanisms represented by the mantle-plume activity. Methane emission from magma, thermal decomposition of pre-existing organic matter and serpentinization of oceanic crusts are considerable factors for the methanogenesis in the early Precambrian oceans. Large-scale activity of methanotrophic micro-organism has not been recorded in marine sediments after 2.1 Ga. This is probably related to the decrease of global volcanism and complete transition of the marine primary producer to photo-synthesizing micro-organism.

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