On idaite (Cu5FeS6) in Japan

The authors have arrived at the following results upon studying the idaite-bearing ores from ten different localities in Japan. 1) Idaite have been found in several deposits in Japan. The specimens from Yakuwa Mine, Yamagata Prefecture, have been unequivocally identified by X-ray powder method. The number of sites yielding idaite in Japan is expected to increase with further study. 2) Idaite occurs in the secondary enrichment zone of copper deposit in the form of secondary decomposition product of chalcopyrite and bornite, except in two sites, where it is present as final crystallization product in copper deposits formed under low temperature and pressure. 3) Hypogene idaite is contained in small quantity in bornite, together with digenite and chalcopyrite. Supergene idaite forms lattices, lamellae and veinlets buried in chalcopyrite and bornite. In some cases, it forms films between chalcopyrite and supergene chalcocite, or replaces pyrite in company with supergene chalcocite, digenite and covellite. 4) The process of secondary enrichment and oxidation of chalcopyrite and bornite may be summarized as follows; chalcopyrite→supergene bornite hypogene bornite idaite chalcocite digenite→covellite cuprite tenorite native copper