Industrial Mineral Resources in the Ube District, Yamaguchi Prefecture (1st report) : The Clay Resources in the Western Area of Ube

Tertiary and Quarternary sediments, Kotogawa conglomerate and Uve coal-bearing formations and Kotozaki formation, are distributed widely in the western area of Ube district. In these formation, seven clay or clayey shale beds are found, and named succesively from lower to upper stratiformations A, B, C, D, E, F, and G-bed for convenience. Four beds among them are now being used as industrial raw material. That is, A-bed and C-bed are being mined for the raw material of a crude pottery such as roofing tile, earthen pipe, brick, etc., and B-bed and F-bed for that of cement. A-bed which belongs to the lowest part of the Ube coal-bearing formation is a while or bluish gray clay layer with 1 to 5 meters in thickness and mainly consists of kaoline group minerals such as halloysite, hydro-halloysite and kaolinite. B-bed is a weathered sandy shale, 15 to 25 meters in thickness, having within itself two coal seams called Sanjaku and Futadan. Containing a considerable amount of sandy materials, this bed mainly consists of montmorillonite, kaoline group minerals and sericite. Among them montmorillonite is the richest. C-bed, white clay bed with 1 to 2 meters in thickness, lies in the middle part of Ube-coal-bearing formation and has nearly the same mineral composition as A-bed. F-bed, occurring in the boundary between middle and upper parts of Ube coal-bearing formation, consists of coaly and weathered sandy shales, an clay mineral in the bed is mainly montmorillonite like in B-bed. In the district, B-bed is the most important as a clay raw material for cement, because of its thick layer and wide distribution. Mean chemical composition of this bed is similar to the clay raw material being used in the cement industry of Japan as seen in Table 3.