The Journal of the Japanese Association of Mineralogists, Petrologists and Economic Geologists
Online ISSN : 1883-0765
Print ISSN : 0021-4825
ISSN-L : 0021-4825
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Volume 45, Issue 6
Displaying 1-5 of 5 articles from this issue
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  • Thermal transformation of bementite
    Kenzo Ito
    1961 Volume 45 Issue 6 Pages 209-218
    Published: June 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.209
    JOURNAL FREE ACCESS
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    Thermal transformation of bementite in air has been studied minutely in the temperature range up to 1200°C, using the differential thermal, thermogravimetric, chemical, and X-ray analyses.
    A correlation of thermal and chemical data with phase determinations shows that the chemical reactions caused thermally are dehydration, oxidation of a part of Mn2+, to Mn4+, and reduction of Mn4+ formed at the former stage to Mn2+, in order of increasing temperature, and bementite transforms, in general, into braunite at the low-temperature oxidation stage and into two phases, i. e. rhodonite and hausmannite, at the high-temperature reduction stage.
    The braunite formed at the low-temperature oxidation stage contains a greater amount of SiO2 in its structure than naturally occuring braunite.
    At the high-temperature reduction stage, quartz, if it is present, combines with hausmannite released from braunite and forms rhodonite. This reaction promotes the decomposition of braunite.
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  • Mineralogical studies on todorokite and birnessite from the todoroki mine, Hokkaido
    Yu Hariya
    1961 Volume 45 Issue 6 Pages 219-230
    Published: June 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.219
    JOURNAL FREE ACCESS
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    Todorokite and birnessite from the Todoroki mine, Hokkaido, Japan were studied by electron micrographs, X-ray and differential thermal analysis. Electron micrographs of todorokite show the crystals to be thin plates flattened on {001}. Many of the plates are broken into narrow laths or blades which are elongated parallel to the b axis. It appears as though the crystals have two perfect cleavages parallel to {001} and {100}. D. T. A. curve of todorokite is characterized by a endothermic peaks at 104°C, 280°C, 480°C, 508°C, 545°C and 680-880°C. D. T. A. curve of birnessite is characterized by a endothermic peaks at 120°C, 260°C, 540°C and 680°C. Electron micrographs of birnessite show the crystals thin plates and needle shape. X-ray powder pattern data correspond to thore which were obtained by other writers.
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  • Some studies on xenoliths from Onigajô, Mié Prefecture
    Kazuo Harada
    1961 Volume 45 Issue 6 Pages 231-238
    Published: June 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.231
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  • Jadeite-bearing rocks in Kamuikotan metamorphic terrain of the Mituisi district, Hokkaido
    Yotaro Seki, Mizuo Aiba
    1961 Volume 45 Issue 6 Pages 239-244
    Published: June 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.239
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    Petrographical descriptions of some samples of the Kamuikotan metamorphic rocks collected from the Mituisi district are presented. These rocks are chiefly composed of jadeite, aegirine, glaucophane, riebeckite, epidote, pumpellyite, chlorite and albite. Besides these minerals, calcite, sericite, stilpnomelane, hematite and leucoxene are also stably found. Though the development of schistosity is weak and the degree of recrystallization is very low, these rocks were almost completely replaced by the mineral assemblages of the lawsonite-pumpellyite-epidote-glaucophane subfacies of the glaucophane schist facies.
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  • Etching figures of silicon crystal
    Keiichi Omori, Makoto Kobayashi
    1961 Volume 45 Issue 6 Pages 245-250
    Published: June 05, 1961
    Released on J-STAGE: August 07, 2008
    DOIhttps://doi.org/10.2465/ganko1941.45.245
    JOURNAL FREE ACCESS
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