Density separation, also known as gravity separation or specific gravity separation, is a mineral processing technique that exploits differences in the density (specific gravity) of minerals to selectively separate valuable ore minerals from gangue (waste) material. It is one of the oldest and most widely used beneficiation methods in mining and remains a cornerstone process in bauxite, gold, iron ore, and diamond processing operations worldwide. The fundamental principle underlying density separation is that when mineral particles of differing densities are subjected to gravitational or centrifugal forces — often in the presence of a fluid medium — they stratify or segregate according to their specific gravity. Dense minerals settle faster or are displaced differently than lighter gangue minerals, enabling their physical separation. In diamond mining, dense medium separation (DMS) is the primary recovery technique, exploiting the high density of diamonds (approximately 3.5 g/cm³) relative to kimberlite and other waste minerals. A ferrosilicon and water suspension is prepared to a density intermediate between diamonds and gangue, causing diamonds to sink while lighter material floats. In gold operations, gravity separation using jigs, spirals, and shaking tables recovers coarse, free-milling gold ahead of cyanide leaching. In iron ore processing, spirals, jigs, and DMS cyclones separate high-density hematite and magnetite from lower-density silica and alumina gangue minerals. In bauxite beneficiation, density separation is employed to remove coarse silica and laterite fractions from the valuable gibbsite, boehmite, and diaspore ore minerals.
