Mineral processing refers to a number of interrelated procedures that are all aimed at extracting valuable material from ores. Many valuable minerals are mined as ores, which are rocks that contain useful substances. Mineral processing was done by hand in the past, though in modern times it is typically achieved through the use of heavy machinery. There are four main types of mineral processing, each of which uses a different method to separate valuable materials from ore gangue. The four different methods involve the reduction of ore particle sizes, the separation of particles by size, concentration of wanted minerals, and the removal of liquids from the solid minerals.
Early mineral processing typically involved manual labor, such as striking ore with hammers to break it open. This process of separating minerals from ore by hand was known as spalling. Similar processes were developed during the 10th century that mechanized the use of hammers to break the ore. These stamp mills typically used a water wheel to lift the hammers and the force of gravity to draw them down onto the ore. Early processing techniques also relied on manual labor to pick out each individual mineral particle from the ore gangue.
Modern mineral processing techniques typically use mechanized unit processes to separate minerals from ore. The first process is typically comminution, which can consist of crushing or grinding an ore. This procedure can break minerals out of the ores, allowing them to be further processed. The next step may be to separate out the particles according to size. One common way this can be accomplished is through the use of progressively finer screens.
After the ore has been broken down and sorted by size, it may undergo one or more processes to separate desired minerals from unwanted ore gangue. The specific processes may vary between different minerals, and are highly dependent on the physical qualities of both the mineral and ore. Gravity concentration is a relatively simple method that works due to the different specific gravity of each mineral and ore. This is a relatively low tech method and one of the earliest used. It typically involves placing the mineral and ore into a container and shaking it until the different materials have settled separately.
The final procedure in mineral processing is often dewatering, which separates moisture from the minerals. This may be achieved by passing the minerals over specialized screens, or through other methods. Particular minerals, such as metals, may undergo additional processing methods. Metals may be subjected to a variety of pyrometallurgical mineral processing techniques, such as smelting.