The simplest of the gravity separation processes used to concentrate minerals before their final grinding and liberation. It is also used to separate coal from the heavier shale. Heavy media of suitable density are used, in which lighter minerals float and denser minerals sink. In industry, the medium is usually a thick pulp made from a heavy mineral in water. Dense-medium separation is suitable for any ore which has enough difference in specific gravity between waste and mineral particles to repay the cost of treatment.