<報文>耐火粘土の鉱物学的研究(第1報) : 福島県高湯温泉付近小岩沢産の加水ハロイサイトについて

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The refractory clay deposits at Koiwazawa near Takayu, Fukushima prefecture, are considered to have been formed as alteration product of andesitic tuff-breccia by the hydrothermal action of sulphate solution. The refractory clay ores are pale brown or pale gray and consists of hydrated halloysite associated with a small quantity of pyrite, limonite and unaltered feldspar. In some parts of the deposits, white hydrated halloysite occurs as irregular masses filling cavities and interspaces of the ore body. This hydrated halloysite is white or very pale greenish white, soft and greasy, and show colloform banding, which is indicative of a precipitation product from the hydrothermal solution. In this report, precipitatable hydrated halloysite was examined by electron micrograph, X-ray diffraction, chemical and differential thermal analyses. The electron micrograph shows aggregates of fine particles with elongated forms about 0.08 to 0.2μ in length. The X-ray diffraction data, differential thermal analysis curve and chemical composition are in good agreement with typical hydrated halloysite given in the literature. The result of the thermal transformation experiment is as follows : At 200℃, the basal diffractions were shifted to smaller spacing ; for instance, 10.3A spacing reduced to 7.46A, while (hk) reflections remained unchanged. At 600℃, all of these diffraction lines disappeared, and only a very diffused band with its peak near 4.2A was detected. At 1,000℃, some very faint lines corresponding to γ-Al_2O_3 were observed, but it is not necessarily an evidence of the formation of γ-Al_2O_3 ; on the other hand, the band remained unchanged. On further heating to higher temperatures, only mullite-like phase appeared at 1,200℃, and no cristobalite was formed up to 1,300℃. Accordingly, for this specimen the sharp exothermic reaction at 950℃ seems to be explained by the formation of nuclei of mullite-like phase rather than by γ-Al_2O_3 phase.
東北大学の論文
1966-03-15

<報文>耐火粘土の鉱物学的研究(第1報) : 福島県高湯温泉付近小岩沢産の加水ハロイサイトについて

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