 Mineral processing (or mineral dressing) is a specialized area in the science of metallurgy that studies the mechanical means of crushing, grinding, and washing that enable the separation (extractive metallurgy) of valuable metals or minerals from their gangue (waste material).Processing of placer ore material consists of gravity-dependent methods of separation, such as sluice boxes.Only minor shaking or washing may be necessary to disaggregate (unclump) the sands or gravels before processing.