Electro-magnetic method : The method is used if the gangue or the ore particles are magnetic in nature. The Finely prwdered ore is dropped on a belt moving on two strong electromagnetic rollers. The magnetic and the non-magnetic substances form two separate heaps. for example ,let the ore particles be magnetic and then the non-magnetic roller.
Eg : Haematite and magnetic hae magnetic ore particles. cassiterite or Tin stone has wolframite as magnetic impurity.
