Mining

Mining is the process by which ores or related materials are extracted from the Earth. Ore is defined as a rock or mineral, generally metallic, which can be mined, processed, transported, and sold at a profit. Therefore, the classification of an Earth material as ore depends as much on economics and technology as geology. Nonmetallic substances that are commonly mined but not considered to be ores include coal, phosphate, and sand and gravel. The term groundwater mining is sometimes Earth movers strip mining for coal in West Virginia. Photograph by Chris Jones. Stock Market. Reproduced by permission. used to describe the withdrawal of groundwater from an aquifer more rapidly than it is recharged by infiltration or underground flow from adjacent areas.

Mining can occur either at Earth's surface in strip mines or open pit mines, or beneath the surface in underground mines. The method used depends on the depth, lateral extent, and economic value of the rock being mined. The deepest underground mine on Earth, which is 2.4 mi (3.8 km) deep, is a South African gold mine. The open-pit Bingham Canyon Mine near Salt Lake City, Utah, is more than 2.5 mi (4 km) wide and more than 0.62 mi (1 km) deep. It is the largest man-made excavation on Earth. Excavation of the pit began in 1906 and has continued into the early twenty-first century, producing primarily copper with smaller amounts of gold, silver, and molybdenum.