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.