Answer. The process of removal of gangue from the ore is technically known as concentration and the purified ore is called the concentrate. The concentration process used in metallurgy of copper is froth flotation. It is based on the wetting characteristic of the ore and the gangue particles with oil and water, respectively.
The ore particles are preferentially wetted by oil and the gangue particles by the water. The whole mixture is agitated with compressed air. Hence, oil coated ore particles being lighter come to the surface in the form of a froth that can be skimmed as shown in figure below.