In electromagnetic processing, the mechanical separation of mixed, finely comminuted minerals is carried out using the attractive effect of strong magnets excited by an electric current. This process enriches valuable mixtures by separating out harmful or worthless components. Magnetically separable materials include all iron ores and other ores with certain contents of iron, nickel, cobalt, titanium, tungsten, and manganese, such as malachite, copper glaze, copper ore, chalcopyrite, pale ore, some zinc blende, monazite, and apatite. Additionally, manganese-ferrous silicates, phosphates, and carbonates, as well as ferruginous rocks like slate, serpentine, and dolomite, can also be separated by a magnetic current. The present volume is illustrated with 46 black and white illustrations. This is a reprint of the original edition from 1903.