Coal mining is the process of extracting coal from the ground.
Coal is valued for its energy content, and, since the 1880s, has been widely used to generate electricity.
Coal mining processes are differentiated by whether they operate on the surface or underground.
Many coals extracted from both surface and underground mines require washing in a coal preparation plant.
This is accomplished by drilling holes into the overburden, filling the holes with explosives, and detonating the explosive.
The overburden is then removed, using large earth-moving equipment, such as draglines, shovel and trucks, excavator and trucks, or bucket-wheels and conveyors.
Technical and economic feasibility are evaluated based on the following: regional geological conditions; overburden characteristics; coal seam continuity, thickness, structure, quality, and depth; strength of materials above and below the seam for roof and floor conditions; topography (especially altitude and slope); climate; land ownership as it affects the availability of land for mining and access; surface drainage patterns; ground water conditions; availability of labor and materials; coal purchaser requirements in terms of tonnage, quality, and destination; and capital investment requirements.
International trade expanded rapidly when coal-fed steam engines were built for the railways and steamships.The choice of mining method depends primarily on depth, density, overburden and thickness of the coal seam; seams relatively close to the surface, at depths less than approximately 180 ft (55 m), are usually surface mined. coal that occur at depths in excess of 200 ft (60 m) are mined by the open pit methods, due to thickness of the seam 60–90 feet (20–25 metres).Coal that occurs at depths of 180 to 300 ft (55 to 90 m) are usually deep mined, but in some cases surface mining techniques can be used. Coals occurring below 300 ft (90 m) are usually deep mined.When coal seams are near the surface, it may be economical to extract the coal using open cut (also referred to as open cast, open pit, mountaintop removal or strip) mining methods.Open cast coal mining recovers a greater proportion of the coal deposit than underground methods, as more of the coal seams in the strata may be exploited.Strip mining exposes coal by removing earth above each coal seam.This earth is referred to as overburden and is removed in long strips.The coal is then loaded onto large trucks or conveyors for transport to either the coal preparation plant or directly to where it will be used.Most open cast mines in the United States extract bituminous coal.Steel and cement industries use coal as a fuel for extraction of iron from iron ore and for cement production.In the United Kingdom and South Africa, a coal mine and its structures are a colliery, a coal mine a pit, and the above-ground structures the pit head.