These machines have powerful electromagnets in a wedge section. The material is
treated on rolls on which magnetism is induced; they consist of alternate disks
of soft iron and some nonmagnetic material. The ore is fed over the first roll,
which removes the most magnetic material, and the tailings go on to the second,
which is weaker, where a second separation is made. Liddell
Source:
Dictionary of Mining, Mineral, and Related Terms
