Mineralogical Journal
Online ISSN : 1881-4174
Print ISSN : 0544-2540
ISSN-L : 0544-2540
Volume 9, Issue 1
Displaying 1-4 of 4 articles from this issue
 
  • Statistical mode of stacking sequence in a valuevite crystal as deduced by computer simulation
    T. OHTA, Y. TAKÉUCHI, H. TAKEDA
    1978 Volume 9 Issue 1 Pages 1-15
    Published: 1978
    Released on J-STAGE: March 31, 2007
    JOURNAL FREE ACCESS
    Achmatovsk valuevite, Ca0.99(Mg2.20Fe2+0.14Al0.70) (Al2.77Si1.23)·O10(OH)2, a=5.21(1)Å, b=9.00(4)Å, c=9.83(4)Å, β=100°10(6)′ (for 1 M subcell), exhibits X-ray diffraction patterns which assume, unlike common xanthophyllites, a 2 M1 type. A salient feature was observed in the diffraction patterns that reflections with k≠3n are drawn out along c*, and that the diffuse maxima are slightly but significantly displaced from the positions expected for those of a regular 2 M1 structure, showing that the structure is based on a statistical mode of layer sequence. By comparing observed periodic intensity distribution function with ones calculated based on the computer-generated random models of long-period polytypes, which consist of around 100∼150 layers, we have been successful in deriving the probable model for the layer sequence. It is based on the 2 M1 type but faults based on the stacking mode of 1 M occur with a probability of ∼0.1. A notable feature of the model is that the stacking-fault vectors align in only one direction.
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  • Shoji HIGASHI
    1978 Volume 9 Issue 1 Pages 16-27
    Published: 1978
    Released on J-STAGE: March 31, 2007
    JOURNAL FREE ACCESS
    Mineralogical properties of two dioctahedral mica minerals with ammonium ions, collected from Ohgidani pottery stone deposit, Ehime Prefecture, are presented in comparison with those of a dioctahedral potassium mica mineral.
    The two minerals with ammonium are characterized chemically by containing about 2 weight per cent of (NH4)2O and low amount of potassium, and yield four characteristic infrared absorption bands in the region from 3400 cm−1 to 2800 cm−1 and one band at 1430 cm−1. Thermal analysis reveals that ammonium ions are driven off above 400°C before dehydroxylation of 2: 1 layer. They have larger basal reflection spacings and stronger first basal reflection than those of the potassium mica mineral, which can be explained by their bearing of interlayer ammonium in approximately equal amount to potassium.
    No evidences to support the presence of hydronium ions in the present specimens have been obtained.
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  • Matsuo NAMBU, Katsutoshi TANIDA, Tsuyoshi KITAMURA, Eiichi KATO
    1978 Volume 9 Issue 1 Pages 28-38
    Published: 1978
    Released on J-STAGE: March 31, 2007
    JOURNAL FREE ACCESS
    Jôkokuite, MnSO4·5H2O, is a new hydrous manganese sulfate discovered at the drift wall of the 50 m level of the Jôkoku manganese-lead-zinc mine, southwestern Hokkaido. It occurs as post-mine stalactites up to about 5 cm long and 1 cm across, apparently precipitated secondarily from mine waters carrying components from manganese carbonates consisting mainly of rhodochrosite and manganoan calcite.
    X-ray powder diffraction pattern shows that it is triclinic with a=6.37Å, b=10.77Å, c=6.13Å, α=98°46′, β=109°58′, γ=77°50′, Z=2, and space group P-1 seems probable from the analogy with chalcanthite (CuSO4·5H2O). Wet chemical analysis gives the formula of (Mn0.93Fe0.04Zn0.03)1.00S1.00O4.00·5.07H20, or ideally MnSO4·5H2O. Therefore, this is the manganese analogue of chalcanthite, pentahydrite and siderotil.
    The mineral is pale pink with vitreous luster, and transparent to translucent. Streak is white. No discernible cleavage. Mohs hardness of aggregates is about 2.5. Specific gravity is 2.03 (meas.) and 2.094 (calc). It is biaxial and optically negative, 2V about 70–80°, dispersion very weak. The indices of refraction are α=1.498, β=1.510, γ=1.517, all±0.003.
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