Refining (as in non-metallurgical uses) consists of purifying an impure material, in this case a metal. It is to be distinguished from other processes such as
smelting and
calcining in that those two involve a chemical change to the raw material, whereas in refining, the final material is usually identical chemically to the original one, only it is purer. The processes used are of many types, including
pyrometallurgical and
hydrometallurgical techniques.