Cyclone washing of small coal originates from the Netherlands. Clean separation is effected with the aid of centrifugal force. The heavier shale particles move to the wall of the cyclone and are eventually discharged at the bottom while the lighter coal particles are swept toward the central vortex and are discharged through an outlet at the top. The washer may be used for cleaning coal up to 3/4 in (1.9 cm). The coal is normally deslimed at about 0.5 mm before cleaning. The separating medium is water and ground magnetite, the bulk of which is recovered and returned to the circuit. A 20-in (50.8-cm) cyclone has a feed capacity of about 50 t/h of coal sized between 1/2 in (12.7 mm) and 1/2 mm.