Ore Concentrating

—In mining, the proce of sorting ores according to richne or of separating the metallic portions of powdered ores from the gangue. There are two proce es, the dry and the wet. In the dry proce , the main principle is a blast of air, carrying or blowing the ores according to their weight, the quantity of metal determining the relative weight. According to their weight, the ores fall down and are thus separated, the very light parts being blown away as dust. In the wet proce , the ore is put in a machine which has a circular, concave grooved disc, with a continuous rotary motion. The ore and water are received at the center and carried by centrifugal force to the rim of the disc, the heavier particles settling in the rifles. The debris, separated by the current and constant agitation, is carried out by the sluice acro the disc to the center, and is discharged through openings into the stationary circular sluice below.