Separation and Concentration Techniques

The separation and concentration of the valuable mineral can take place after the ore is crushed, ground, and classified into the required particle size distribution. There a number of different techniques are employed in concentrating the valuable minerals. These techniques exploit differences in physical or chemical properties of the valuable and gangue minerals.

Basically, there are four kinds of separation and concentration techniques:

i. Sorting – based on appearance, colour, texture, optical properties and radioactivity

ii. Gravity and Dense-Medium Separation – Separation based on specific gravity of the valuable mineral relative to the gangue and the carrying medium such as water. In dense-medium separation, the a carrying medium is a mixture of water, magnetite, or ferrosilicon. The paramagnetic properties of the medium allow it to either remain in suspension at a predetermined slurry density or to be separated from water for cleaning and reuse.

iii. Magnetic Separation – separation based upon natural or induced differences in magnetic susceptibility of the minerals within the ore.

iv. Froth Flotation – separations based on the surface chemistry properties of a mineral. The natural or modified surface property of the mineral determines its ability to attach to an air bubble and float to the surface.

Mineral Concentration


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.