Bismuth minerals from the Fukueison mine, Yamagata Prefecture, Japan

Abstract

Bi minerals have been discovered from the Fukueison mine, situated in the Uetsu region, Tsuruoka City, Yamagata Prefecture, Japan. Bi minerals occur in quartz veins which consist of chalcopyrite, pyrite and chlorite, accompanied by minor molybdenite, sphalerite and arsenopyrite, hosted in the Nishitagawa granodiorite. Bi minerals are composed of bismuthinite as a major constituent and native Bi, Bi-sulfosalts (krupkaite, cosalite and galenobismutite) and Bi-Te-S minerals (tetradymite, joseá ite-A, joseá ite-B and ingodite) as minor constituents. From the paragenesis and texture of Bi minerals, these minerals might have been formed by a change of fS2 and fTe2 conditions. Comparing to other Bi-bearing Mo deposits, Inner Zone of Southwest Japan, it is considered that Bi is closely related with Cu mineralization.