天草陶石の構成鉱物

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概要

• 論文の詳細を見る

• The constituent minerals of the ores of the Amakusa pottery stone deposits have been examined by X-ray powder method, electron probe microanalysis, differential thermal analysis, polarizing microscopy, etc. The main constituent minerals of the pottery stones are quartz, sericites and kaolinite. Minor components of them are dickite, rectorite, tosudite, smectite, plagioclase, K-feldspar, calcite, siderite, pyrite, etc., among which the first three minerals occur only in the Sarayama vein. Feldspar, carbonate and pyrite are more abundant in the Kaigan and Murayama veins. X-ray diffraction peaks of the quartz are broard. The cell dimensions are relatively large with a = 4.9137-4.9154A and c = 5.4047-5.4057A at 21℃. Most quartz samples show relatively high Al_2O_3 contents around 0.1wt% up to 1wt% in maximum, and are inhomogeneous in the Al_2O_3 content among grains. The high-low inversion peak in the DTA curve is broad and the peak temperature is lower than that of common quartz. Sericites in the ores of the Sarayama vein comprises coarse-grained 2M_1 and 1M micas and fine-grained irregularly interstratified IM mica/smectite with small amounts of smectite layers. Sericites in the ores of the Kaigan and Murayama veins are mostly coarse-grained 2M_1 and IM micas. These coarse-grained micas often form banded structure in which 2M_1 mica tends to grow inside. Tetrahedral and interlayer compositions of the 2M_1 mica are close to those of ideal muscovite although octahedral Fe and interlayer Na are appreciably contained. The IM mica and fine-grained irregularly inter-stratified IM mica/smectite have less tetrahedral Al and interlayer cations, and the contents of octahedral Fe and interlayer Na are very small. Such a difference in chemical composition between 2M_1 and IM micas is most pronounced in those of the Sarayama ores. The observed variations of sericites in chemical composition, polytype and interstratification are discussed with their genesis.

• 日本粘土学会の論文
• 1988-06-10

著者

• 中川 昌治

  高知大学理学部

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