Apparatus for the separation of heavy and light particles from particulate material which includes means for fluidising and agitating the material to cause heavy particles to sink from the acceptable material and comprising a deck adapted to receive material at a reception end and means for vibrating said deck to cause the material to move longitudinally along it to a discharge end, said deck having a number of longitudinally extending troughs separated by peaks and providing an upwardly directed air flow in the troughs characterised by control means for causing the velocity of the upwardly directed fluidising air in each trough to initially increase to a point below the peaks and to then continue upwards at a reducing velocity.