Fundamental Studies on the White Clays in South Kyushu

Abstract

White clay resources are very abundant in South Kyushu, though very little have ever been reported on them except the well-known “Ibusuki clay”. The object of this paper is to describe the results of the writers works on the fundamental properties of four kinds of the white clays, namely those produced in Kirishima, Iriki, Okuchi, and Masaki.
The clays here selected are all of vast resources and exceptionally poor in iron.
Grading analysis, chemical analysis, various thermal tests, X-ray analysis, electron-microscopic survey etc. were conducted on these clays, with the results as follow:
(1) It is very likely that the main component mineral of these clays is hydrohalloysite. The mineral composing Masaki, Iriki, and Kirishima clays, all of which are presumed to be of hydrothermal origin, shows a tubular shape under the electron-microscope. On the other hand, the one contained in Okuchi clay, which was derived from tuff through superficical weathering, appers as a rounded granule without any linear outline.
(2) Iriki clay is comparatively coarse-grained, while Kirishima and Masaki clays are rather fine-grained. Okuchi clay is so fine-grained that 75% of the component minerals are less than 2μ in diameter.
(3) All of the four clays are very high in refractoriness, while the burning colours of Masaki and Iriki clays are snowy white. Thus the two clays are considered to be very suitable for the raw materials of ceramic wares.
(4) When burnt up to 1000°C, the coefficients of contractions of Iriki, Okuchi, and Masaki clays were almost similar, about 7.0%, while that of Kirishima clay showed a lower value, 5.6%.