北海道, 下川鉱床産鉱石鉱物のコバルト濃度について

抄録

The high grade of cobalt characterizes the deposit of the Shimokawa copper mine which is one of the most famous bedded cupriferous pyrite deposits of Japan. Unfortunately, however, the cobalt has not been recovered, because the concentration of cobalt is difficult. In order to show the distribution of cobalt in the ore, the microscopic observation and the electron microprobe analysis have been carried out. The main ore minerals are pyrite, chalcopyrite, monoclinic pyrrhotite, sphalerite, cobalt pentlandite, and cobaltian mackinawite in the descending order of abundance. Among them, pyrite is the most important carrier of cobalt, and cobalt pentlandite is subordinate. The cobalt of the copper concentrate depends upon the small mingled grains (less than 20μm) of cobalt pentlandite which is closely associated with chalcopyrite. On the other hand, the pyrite concentrate owes its cobalt amount to cobalt-rich pyrite. On the basis of the texture of ore and the crystal form of pyrite, the mode of occurrence of pyrite is divided into seven types as shown in Figs. 1 (a)-(g). The R-type pyrite having a rounded form is the richest in cobalt among them, and contains a average cobalt concentration of 0.8 wt.%.These natures of ore suggest that the cobalt of the coppem concentmate may be recovered as a by-pmoduct of the copper smelting, and that the cobalt of the pyrite concentrate may be recovered as a cobalt concentrate consisting of R-type pyrite.