A specimen of the so-called ill-crystallized sericite was found associated with the Kuroko ore body of the Shakanai mine. The specimenypgives a 10.3 Å reflection and higher orders, but the hkl reflections are extremely weak and broad. Although the specimen is an interstratified mineral of mica with its expandable layers, the X-ray pattern clearly differs from those of 1 Md mica and the common interstratified minerals. The infra-red, DTA and electron diffraction data are similar to those of a mica clay mineral with 2M polymorph. Chemical composition: SiO₂ 47.53%; Al₂O₃ 37.40%; Fe₂O₃ 0.00%; MgO 0.47%; CaO 0.19%; Na₂O 0.34%; K₂O 7.33%; H₂O⁺ 5.32%; H₂O^-1.47%; Total 100.05%.

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The removal treatment of iron oxide from clay is commonly carried out in air with agitation by using reducing agent, but amount of iron oxide extracted is different with agitating methods.
In this experiment, in order to remove iron oxide from clay, ball mill and glass beaker were used for the reaction chamber with sodium dithionite and sulfuric acid, and the influence of reaction chamber on the extraction of iron oxide from clay was studied.
When removal treatments of iron oxide from clay were carried out with ball mill, it was found that the amount of iron oxide extracted were increased and the amount of reducing agent were lowered in comparison with case of beaker test in air.
The 20 to 30 r. p.m. of ball milling were the optimum conditions and the amount of iron oxide extracted decreased with increasing the number of revolutions by reason of the disproportionation of sodium dithionite.

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Excessive earth pressure occasionally causes much damage to tunnel construction in a serpentinite belt. The geochemical research reported herein was conducted to study the cause of such earth pressure. The following results were obtained:
(1) no clay mineral capable of swelling is included and chryaotile and antigolite are the dominant clay minerals, (2) weathered parts of serpentinite are easily sheared and reduced to flow by a little increase of water, (3) the weathered part, in which clay particles are oriented in a certain direction, is easily sheared in this direction.
Finally, it is suggested that the excessive earth pressure in a serpentinite belt is not attributed to “swell of clay minerals” but to “flow of earth induced by shear of the weathered part”.

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