黒雲母より風化変質によって生成したバーミキュライトの加熱による相変化

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Macroscopic vermiculite derived from biotite by weathering is commonly found in granitic regions of Japan. Such vermiculite was collected from the weathered granitic rook in Senmaya, Iwate prefecture. The X-ray pattern obtained from orientated aggregates of this sample showed weak reflections around 25Å, 12Å, 7Å and a strong reflection around 14.7Å. The reflections around 25Å and 12Å are interpreted as indicating the interstratification of mica and vermiculite. The 7Å reflection is basal reflection of kaolinite and the 14.7Å reflection is that of Al-vermiculite. The pattern shows that the sample is largely composed of vermiculite, while the other minerals are very small in amount. The chemical composition of the sample is rich in Fe_2O_3 but poor in MgO in comporison with the so-called Mg-vermiculite so for known. With the aid of a high temperature X-ray diffraction apparatus, it was confirmed that the basal reflection is continuously, not stepwise, contaacted from 14.7Å to 10.2Å to 11.2Å, as temperature rises from the room- temperature up to 500℃. The X-ray powder patterns of the samples heated at various temperatures suggest that the exothermic peak at about 900℃ corresponds with the decomposition of vermiculite structure followed by the formation of a small amount of hematite. The larger part of the decomposed vermiculite remains unchanged although it is X-ray amorphous at this stage. Cristobalite, hematite, indialite, spinel type oxide, mullite etc. are also formed at the temperatures higher than 1000℃ and they are entirely melted away at 1350℃. In order to study the structural relations between the vermiculite and the afore-mentioned crystals formed above 1000℃, the following experiment was cerried ont; the glass made after melting the vermiculite was reheated and the crystals thus formed were compared with those formed by the heating of the vermiculite as mentioned above. Judging from the results, it seems that there is almost no structural relation between the vermiculite and the crystals which formed above 1,000℃.
日本粘土学会の論文
1971-03-05

黒雲母より風化変質によって生成したバーミキュライトの加熱による相変化

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