Mining: Broadly mining operations can be categorized into surface mining and sub-surface mining.
Surface mining involves stripping of surface vegetation, dirt, and even bedrock if necessary, to reach buried ore deposits. Common techniques of surface mining are open pit mining i.e. recovery of mineral from an open pit and Strip Mining that involves more targeted removal of surface layers to reveal the useful ore underneath.
Sub-Surface Mining involves digging of tunnels and shafts to reach deeply buried ore deposits.
Milling: After ore is extracted from the mine, metal bearing minerals are separated from waste material to form concentrate through a process called milling. This is often a series of chemical treatments processes. Sometimes mechanical processes like gravity separation, buoyant separation, centrifugal and magnetic separation are also employed but the scope of application of such processes is rather limited.
Smelting and Refining: After milling, Ore concentrate undergo smelting and refining to extract metal content from its ore. While a no. of different methods can be used for this the most widely used method for smelting is chemical break down of mineral through heating and melting. Specific smelting methods are devised for different kind of ore concentrates. Output of smelting is impure metal that is sent to refinery for purification.