栃木県葛生地域よりのセピオライトのあらたな産出

概要

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A new occurrence of white clay-vein consisting almost entirely of well-crystallize sepiolite along the fault running through the Upper Limestone Member of the Nabeyama Formation in the Kuzu district is shortly reported. Field observation and its mineralogical studies led to the following results; 1) the vein runs N80°E, with dip 40°NW, and the width usually ranges from 6 cm to 10 cm, but the maximum attains 25 cm. the contact between the vein and the wallrock is sharply defined. And it often contains lenticular masses of microcrystalline quartz. 2) the result of the chemical analysis of minus 2 microns fraction of the present material is generally in good agreement with the pablished data of common α-sepiolite as listed in Table 1. the structural formula of "dehydrated sepiolite" calculated from the result on a basis of Brauner-Preisinger model was as follows: (Al_<0.06>Fe^<3+>_<0.01>Mg_<7.89>)_<7.96> (Si_<11.79>Al_<0.21>)_<12>O_<32>・Ca_<0.21> 3) x-ray diffraction patterns of the present material unheated and heated at various temperatures as shown in Fig. 5 clearly indicated that the material is a well-crystallized sepiolite. 4) Thermograph of the present sepiolite clearly showed four steps of dehydration, in the temperature ranges of <250℃, 250°~450℃, 450°~610℃ and 730°~860℃. the total weight loss of the second and third steps is nearly twice as much as the final weight loss.
日本粘土学会の論文
1966-12-05