<Contributions>Investigation in Heavy-Media Separation at the Ashio Copper Mine

The fundamental research in heavy-media separation was started in May, 1949. The industrialization of the results of the research was planned and followed by the actual operation. The summary of the fundamental research is as follows : -(1) The floatability of gangue mineral in heavy suspension varies with the character of mineral. The gangue mineral of angular form is more floatable than of flat form, and that of rough surface is more floatable than that of smooth surface. (2) There are certain limitations in the range between the maximum and minimum sizes of feed. The small sized feed is more floatable than the large sized one owing to the decrease in settling velocity. Consequently, the grade of float product is apt ot rise and the result of separation may be lowered as a whole. (3) The floatability is high when the particle size of suspension medium is coarse and it decreases when the particle size becomes fine. But the separation seems to be better in the suspension medium of minute size. The conclusion upon the size range of the suspension medium has not yet been obtained, as the particle size of the medium has a bearing on the viscosity of heavy suspensions. (4) The sink-and-float phenomena are recognized with the difference of about 0.002 in specific gravities of sink and float. Therefore, for copper ores, it may be possible to separate the float of less than 0.10% Cu. (5) In the Ashio copper mine, it is possible to reject about 70% of float containing less than 0.10% Cu in liparitic raw ore by the heavy-media separation. The results of separation is irregular in quartzitic ore owing to its texture. It may, however, be possible to reject about 60% of float containing less than 0.1% Cu from the feed prior to ball mill grinding