Abstract: Apparatus for separating a comixture of light and heavy materials includes a drum divided into two sections. In the first section, the material is introduced with a fluid, and separated from the fluid such that the fluid flows substantially the length of the first section along a "counter flow" path to wash against the material to be separated before overflowing the first section. The material to be separated separates into floating and sinking fractions, the floating fraction overflowing the first section together with the fluid. The sinking fraction is carried by a scroll along the wall of the first section to be lifted into the second section.In the second section, the sinking fraction is reduced in size by a charge of grinding balls and lifted and removed from the second section.