5. Dry gravimetric concentration

The separation of minerals according to their density can be achieved using air as the particle suspension fluid. However, this is only a marginal concentration route when it comes to equipment selection, and adoption of these methods remains limited. The subject has often been underestimated by technicians, researchers and operators. The result is a very imperfect knowledge of the principles and mechanisms governing pneumatic gravimetric separation, which is still very much empirical rather than theoretical. Pneumatic separation has a long history, mainly in agriculture, where winnowing is a typical example.