Abstract: In an ore cleaning process the underflow from an ore classifying cyclone is delivered to a heavy medium cyclone where the ore is cleaned. The underflow leaving the classifying cyclone is continually measured for specific gravity and flow rate while the specific gravity of heavy medium that can be applied to the underflow is continually measured. The amount of this heavy medium and the amount of water required to be added to the underflow are continually controlled as functions of the specific gravity and flow rate thus measured, whereby a substantially constant specific gravity and flow rate of the underflow is maintained as it enters the heavy medium cyclone. Magnetic separating means receive the overflow from the heavy medium cyclone and separate the heavy medium from the ore, while other magnetic separating means receive the underflow from the same cyclone and separate the heavy medium from the rejects. The heavy medium is used again.