High-grade Uranium Ore Body Newly Discovered at Ningyô-tôgé

The result of uranium prospecting for economic development since 1963 has shown that Ningyô-tôgé and its vicinity on the boundary of Okayama and Tottori Prefs, the region composed of Misasa Group of Neogene Tertiary, have the industrial possibilities from the viewpoint of their grade and ore reserves. Ten uranium ore bodies or so were already found and their ore reserves were also grasped (ore reserves of each body: less than several hundreds thousand tons, their average grade: about 0.06% U3O8). It is said that this average grade is lower than those of foreign countries. Recently, the continuous distribution of high-grade uranium ore body over 8, 000 m2 was discovered in the south gallery of Nakatsugo, Ningyô-tôgé mine where the intensive prospect by tunnelling had been put under way. It is confirmed that its average grade is 1%, the thickness of the mineralized layer is 0.65 m and the amount of uranium metal is more than 100 t. Such a rich uranium ore body is very in the world. In this paper, the outline of this significant ore body is presented.