A cylindrical dense-medium washer developed in the United States. It uses a magnetite water suspension as medium. The bath resembles a drum in shape, its longitudinal axis being horizontal; within the stationary outer casing there is a rotor divided into compartments. Raw coal is fed near the top of the separator, and separation takes place as the rotor revolves. The machine produces clean coal and shale; the magnetite is recovered. It can handle coal up to 10 in (254 mm) in size, the lower limit being about 1/4 in (6.4 mm). Magnetite consumption runs at about 1/2 lb/st (0.25 kg/t) of feed.