LAP04840 is an unusual R chondrite that includes abundant hornblende amphibole. LAP04840 shows a texture of equilibrated chondrite composed of 59.3% olivine, 13.5% orthopyroxene, 13.3% hornblende, 6.2% plagioclase, 6.0% Fe-Ni sulfide, and 1.7% accessory minerals. Hornblende replaces olivine and pyroxene in both chondrules and matrices, suggesting its secondary origin. All major phases in LAP04840 are homogeneous: olivine (Fa₃₇), orthopyroxene (En₇₀Wo₁), and plagioclase (An₈Or₂). Hornblende is also nearly homogeneous, but the total sum by electron microprobe analysis is 96-98 wt%, suggesting the presence of Fe³⁺ and a hydroxyl group. Synchrotron Fe-XANES analysis gives a Fe³⁺/ΣFe ratio of ∼ 0.6 and micro-FT-IR analysis confirms the presence of a hydroxyl group. Thus, the structural formula is (Na_0.40K_0.04)(Ca_1.46Mn_0.02Fe²⁺_0.06Na_0.46)(Al_0.08Fe²⁺_0.43Fe³⁺_0.75Cr_0.08Mg_3.60)(Si_7.02Al_0.98)O₂₂(OH)₂. Single crystal X-ray diffraction of LAP04840 hornblende gives the following lattice constants: a = 9.7957(9) Å, b = 18.0788(12) Å, c = 5.2949(5) Å, β = 104.747(3)°. The relatively short distances of [M(1)-O = 2.069 Å], [M(2)-O = 2.081 Å], and [M(3)-O = 2.058 Å] suggest the feasible preference of small Fe³⁺ at these sites. The mineralogy and petrology of LAP04840 are consistent with its classification as an R6 chondrite. However, the presence of hornblende and biotite is quite unique among not only R chondrites but also asteroidal meteorites in general. The presence of these hydrous minerals suggests metamorphism under high pressure and an aqueous environment probably at depth in the parent body. A thermometer using hornblende and plagioclase equilibria gives T = 670-690 °C. Further, a barometer using Al content in hornblende gives P = ∼ 0.1 GPa. Although these estimates bear some uncertainties, it is likely that the size of the R chondrite parent body was large enough to induce such metamorphism.

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Strontium isotopic analysis was carried out on magmatic apatite in the Kamihara Tonalite obtained from the Cretaceous Ryoke belt, southwestern Japan. ⁸⁷Sr/⁸⁶Sr isotopic compositions of euhedral apatite indicated that the initial ⁸⁷Sr/⁸⁶Sr ratio (SrI) in the tonalite varies from 0.70695 to 0.70790. This provides direct evidence of SrI heterogeneity in the Kamihara Tonalite. The SrI heterogeneity is inherited to Rb-Sr whole-rock age determination, and makes the age discrepancy between the Rb-Sr age and CHIME, K-Ar ages. By combining the results of the isotopic analysis, knowledge on the whole-rock chemistry, and field observations, it can be inferred that the SrI heterogeneity in the Kamihara Tonalite was caused by the assimilation of high SrI country metamorphic rocks of the Ryoke belt.

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The crystal structure of α´_L-Ca_1.55(4)Sr_0.45(4)SiO₄ was analyzed by single-crystal X-ray diffraction. Refinement with isotropic temperature factors yielded R = 5.4%. The occupancies of the M(11), M(12), M(13), M(21), M(22), and M(23) sites by Sr are 0.40(3), 0.37(3), 0.42(3), 0.11(3), 0.04(2), and 0, respectively. The structure contains SiO₄ tetrahedra in three different orientations. The orientational ordering of the Si(n)O₄ (n = 1-3) tetrahedra accommodates the M(1n)-O (n = 1-3) bond-valence unbalances caused by the ionic radii mismatch and also avoids increasing the O-O electric repulsions between adjacent Si(n)O₄ tetrahedra.

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The chemical compositions of cavansite and pentagonite, in which H₂O contents and vanadium (in an unknown oxidation state) are present, were determined by thermogravimetry-differential thermal analysis (TG-DTA), electron spin resonance (ESR), and electron microprobe analysis (EMPA). Furthermore, the mechanism of dehydration of the minerals and presence of the hydrous species such as H₂O, H₃O⁺, and OH^- in the aforementioned minerals have been investigated by TG-DTA, high-temperature X-ray diffraction (HT-XRPD) analysis, Fourier-transform infrared (FTIR) spectroscopy, and single-crystal XRD analysis. The results of TG-DTA and HT-XRD revealed that no reversible transitions occur between cavansite and pentagonite when they are heated in air and that no intermediate amorphous phase exists in these two minerals. Gradual dehydration of cavansite in the temperature range of 225-550 °C was attributed to the removal of both oxonium (H₃O⁺) and hydroxyl ions (OH^-); the IR absorption bands of cavansite observed at 3186 and 3653 cm^-1 were assigned to H₃O⁺ and OH^- stretching vibrations, respectively. Moreover, the exact distribution of hydrogens in the crystal structure of the cavansite refined in this study was determined by applying the valence-matching principle; the results showed the existence of H₃O⁺ and OH^-. Thus, the structural formula of cavansite should be revised to Ca(VO)(Si₄O₁₀)·(H₂O)_4-2x(H₃O)_x(OH)_x , in contrast to that of pentagonite, Ca(VO)(Si₄O₁₀)·4H₂O. The changes in the ion product constant of water with temperature and pressure suggest that pentagonite is formed when the hydrothermal fluid is in supercritical condition (>300 °C), while cavansite is formed when the hydrothermal fluid is not in supercritical condition. Thus, cavansite is identified as a low-temperature form and pentagonite as a high-temperature one.

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We have developed a method for the quantitative analysis of binary mixtures of minerals using a common Raman microspectrometer having backscattering optical configuration (180° illumination) and a rotating sample stage. Using the averaged Raman spectra of mineral mixtures, the calibration curves of four mixtures of calcium carbonate and silica minerals—calcite and quartz, aragonite and calcite, quartz and cristobalite, and coesite and quartz—are constructed. The calibration curves express the correlation between the weight fraction and the relative intensities of the Raman bands intrinsic to the binary mixture. This technique can be used to map the phase distributions in one or two dimensions across an analytical sample surface and conduct quantitative analyses of samples containing inclusions with dimensions on the order of a few microns.
     As an example of the quantitative analysis using Raman microspectroscopy, the distribution of quartz and cristobalite in a silica nodule in volcanic rock from Akaze, Ishikawa prefecture is investigated. It is confirmed by X-ray diffraction, optical observation, and Raman mapping analysis that microquartz and opal-C are horizontally layered in the silica nodule. The line profile of the Raman spectra across the two regions reveals a sequential change in the weight ratio from quartz to cristobalite.

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