This process is generally used for the concentration of sulphide ores.
For example:
Copper pyrite (CuFeS2], Galena [PbS], Zinc Blende (Zn) etc.
Method:
Water is taken in a big rectangular utensil. In this, powdered ore is mixed and suspension is made. A very small quantity of floatation agents are added. The water is agitated by the blast of air.
Due to which, light particles of sulphide ore carried out to the surface by the foam and from there they are skimmed off. The gangue particles are preferentially wetted by water sinks to the bottom of the tank.
