Mineralogical Journal
Online ISSN : 1881-4174
Print ISSN : 0544-2540
ISSN-L : 0544-2540
Volume 17, Issue 5
Displaying 1-4 of 4 articles from this issue
 
  • Tsuyoshi MOTOYAMA, Masayuki OKUNO, Takeo MATSUMOTO
    1995 Volume 17 Issue 5 Pages 201-210
    Published: 1995
    Released on J-STAGE: March 31, 2007
    JOURNAL FREE ACCESS
    The site occupancies of major and minor elements in two olivines have been determined by ALCHEMI method using only Si atoms as the reference atoms and assuming the homogeneities in the chemical composition. Since Si atoms in many silicate minerals occupy only the tetrahedral sites, they can be used for the reference atoms. Therefore, the analytical technique derived in this study is useful for the determination of the site occupancies not only in olivine in which Mg atoms show ordered distribution but also in other silicate minerals which contain SiO4 tetrahedra. The determined site occupancies for Mg and Fe show weak preferences in M2 and M1 sites, respectively, which are opposite to those reported previously by ALCHEMI method. However the tendency of the preferences of the major elements (Mg and Fe) in this study is in accordance with those obtained by X-ray diffraction method. The site occupancies for minor elements, Mn and Ni, shows strong preferences in M2 and M1 sites, respectively, which are consistent with previous results by ALCHEMI method.
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  • Daiji HIRATA, Hiroyuki YAMASHITA, Isamu IMANAGA, Haruo TAKAHASHI, Akir ...
    1995 Volume 17 Issue 5 Pages 211-218
    Published: 1995
    Released on J-STAGE: March 31, 2007
    JOURNAL FREE ACCESS
    A ferrian manganoan grossular of the chemical composition (Ca,Mn2+)3(Al,Fe3+)2[SiO4]3 with Ca : Mn2+≈2 : 1 and Al : Fe3+ ≈2 : 1 was found in a lower grade metamorphic bedded manganese ore deposit of the Dainichi mine, Hadano City, Kanagawa Prefecture, in association with piemontite of the similar Ca : Mn and Al : Fe3+ ratios, where the metamorphic grade belongs to prehnite-pumpellyite facies. Grossular and piemontite occur as fine disseminations in a metabasite forming the wallrock of ore beds. The co-existence of Mn2+ with Mn3+ favoured the formation of two discrete but chemically related phases after their preferential lodging. Thus, in the grossular-spessartine continuous solid solution series the manganoan grossular with Ca : Mn2+ ≈2 : 1 is to be partnered with a piemontite having Mn3+: (Al+Fe3+) ≈1 : 2 as its oxidized derivative unless minor fluctuations of ratios and OH in the latter are considered. Apart from the occurrence in metabasite, manganoan grossular is found as a massive form involving hausmannite, caryopilite, chlorite, johannsenite, manganoan calcite, and an unknown mineral with the probable chemical formula CaMn3[SiO4]2·H2O. The metabasite and some ores are penetrated by the veinlets of piemontite with lower Mn2O3 contents. The massive manganoan grossular is superficially converted into rancieite through weathering.
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  • Tsutomu KAWAMURA, Shiro KOJIMA
    1995 Volume 17 Issue 5 Pages 219-230
    Published: 1995
    Released on J-STAGE: March 31, 2007
    JOURNAL FREE ACCESS
    The local heating method by a Nd:YAG laser beam was applied to Si wafers to evaluate thermal variations of their optical properties.
    Firstly, the optical properties such as transmittance, reflectance and absorptance for the Nd:YAG laser beam (the wavelength, 1.06 μm), and their variations with temperature ranging from the room temperature to near the melting point (1685°K) were measured. From the results, the variations of the absorption coefficients were derived and correlated with the calculated thermal variation of the energy gap.
    Secondly, the numerical simulations for the temperature distribution, and the temperature gradient distribution on the locally heated specimen by Nd:YAG laser beam were carried out by using Bessel function. The locally generated thermal stress is also discussed.
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  • Taketoshi TANIGUCHI, Masayuki OKUNO, Takeo MATSUMOTO
    1995 Volume 17 Issue 5 Pages 231-244
    Published: 1995
    Released on J-STAGE: March 31, 2007
    JOURNAL FREE ACCESS
    Local structures around Si, Ca, Mg, Co, and Ni atoms in CaMgSi2O6, CaCoSi2O6, and CaNiSi2O6 glasses were investigated by X-ray diffraction, XAFS, and optical absorption spectra measurements. Si–O interatomic distances of these three glasses are 1.62 Å and coordination numbers of Si atoms are 4. Mg–O, Co–O, and Ni–O interatomic distances are in the range of 2.00 to 2.06 Å and coordination numbers of Co and Ni atoms are estimated to be 4 in the corresponding glass. Ca–O distances are in the range of 2.44 to 2.51 Å and coordination numbers of Ca atoms are estimated to be 6 in the three glasses. Similarities of radial distribution functions obtained from X-ray scattering intensities and XAFS spectra indicate that these glasses have a similar structure and similar local configurations of each cation. The coordination numbers of Ca, Co, and Ni atoms and the interatomic distances of Mg–O, Co–O, and Ni–O in the glasses are smaller than those in the corresponding crystals. These results show that interstitial space of SiO4 networks of these glasses is too large for these modifier atoms, and these atoms are located on the place apart from the center of space. The result of optical absorption spectra measurements reveals that the difference of the ligand field stabilization energy of Ni atom between CaNiSi2O6 glass and crystal is larger than that of Co atom between CaCoSi2O6 glass and crystal. This result is related to the difference of the heat of vitrification from these crystals and the different partition of modifier atom into these crystals.
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