In the Wisconsin field, the zinc blende is usually found associated with iron sulphide in the form of marcasite. This ore, after being milled and concentrated at the mines, is sent to separating plants for further treatment by roasting and magnetic separation, inasmuch as the mixed blende and marcasite concentrate, owing to the high iron content, is not suitable for the zinc smelter, and the magnetic separation scheme of separation must be resorted to --page 1
