The second fundamental (main) operation in mineral processing, after the release, or liberation, of the valuable minerals from the gangue minerals, is the separation of these values from the gangue, i.e. concentration. Concentration is usually accomplished by utilizing some specific
difference in physical (or chemical) properties of the metal and gangue compound in the ore.
In concentration the following terms are used:
Head is the feed to a concentrating system.
Concentrate is defined as the valuable mineral(s) separated from ore undergoing a specific treatment.
Tailing is the fraction of ore rejected in a separating process. It is usually the valueless portion, i.e. discard or waste.
Middlings are the particles of locked valuable mineral and gangue, i.e. liberation has not been attained. Further liberation can be achieved by further comminution.
Reconvery is the percentage of the total metal, contained in the ore that is recovered in the concentrate.