Magnetic Separation Method

Some low-grade iron ore can be treated using magnetic separation because all iron minerals are magnetic to some degree. In this process, the crude ore, which may grade less than 30% iron, is mixed with water and ground to a suitable fineness. The pulp is then passed over a revolving magnetic drum, to which the magnetic iron minerals adhere. They are scraped off and retained, while the gangue particles are discarded with the water.

The magnetic portion is dewatered and filtered, but the concentrate produced is too fine to be used in a blast furnace at a steel plant (the destination of most iron), so it is pelletized — mixed with a suitable bonding agent and rolled on a pan or in a drum until marble-sized, iron-rich balls are formed. These pellets are dried and baked, and then shipped out to steelmakers.

Other methods of metal recovery include photometric sorting — where the distinct light-reflection properties of metallic minerals are used to separate them from gangue minerals — and various simple gravity-based processes.