Abstract
Pottery stone occurs at Takehara Mine located in the eastern end of Okayama City. The mineral assemblages of ore consist mainly of quartz-sericite and quartzsericite-albite together with scarce quartz-kaolinite. The deposit is divided into three mineral assemblage zones: namely, a kaolinite zone (quartz-kaolinite ±albite), a sericite zone (quartz-sericite-albite) and an albite zone (quartz-albite-sericite). The albite and sericite zones comprise most of the deposit. The pottery stone in this mine is formed by hydrothermal alteration of Cretaceous rhyolite. K-Ar dating indicates 72-76 Ma for this deposit, which is the same age as the roseki (pyrophyllite) deposit in the Mitsuishi area of Okayama Prefecture.
