The use of naturally occurring microorganisms to dissolve metals from minerals. This biotechnical process, involving bacteria, archaea, fungi, and yeast, can be applied to both sulfide and nonsulfide minerals. At present, bioleaching is employed on a large commercial scale to extract metals from sulfide minerals. See also: Hydrometallurgy; Leaching

Coalbed methane production, sometimes referred to as coal degasification, is the process of extracting natural gas from underground coal formations (seams). This extraction is accomplished with production technology similar to that used in the conventional natural gas industry. The objectives of producing the natural gas from a coal seam are to improve mine safety, to sell the natural gas, or both. See also: Coal; Natural gas

The technical and mechanical activities involved in removing coal from the earth and preparing it for market. Coal mining in the industrialized countries is characterized by the integration of a number of complex systems into a production methodology that varies for surface versus underground mining (Fig. 1). See also: Coal

Exploration for mineral deposits by chemically analyzing sampled rock, soil, vegetation, and other natural materials for trace amounts of the principal and associated elements. By now, most of the easily discovered mineral deposits have been found, making the search for new deposits ever more challenging. In spite of this, worldwide demands are rising for energy, metallic, and nonmetallic mineral resources. Search continues in regions of known mineralization and in areas where deposits are covered by sediment or obscured by vegetation and ice. Geochemical techniques have become an important part of almost all exploration programs. See also: Mineral; Prospecting

The drilling of holes for gathering and evaluating earth materials in order to design and monitor construction projects. Geotechnical data are required for the accurate, safe, and efficient design and construction of buildings, bridges, highways, dams, and mining sites. The data are derived from analysis of soil and rock samples obtained by drilling. Soil sampling usually is done with a split-spoon sampler, a tube that opens lengthwise to remove the sample. Rock cores are obtained by diamond drilling, using a hollow, diamond-embedded drill bit to cut an intact rock sample. The samples are tested in laboratories for compressive and shear strength, grain size, weathering properties, moisture content, and consolidation projections. The results are used to determine the materials' supporting characteristics, ability to resist transmission of fluids as with dams, and ability to stand without lateral support as in highway cuts or quarries. In addition, tunneling and mining are accomplished safely only with an understanding of the properties of the soil and rock above and below the projected opening. In-hole or in-situ testing through boreholes drilled in a formation is done to determine the material's permeability, water yield, movement (with inclinometers), and settlement over time (with settlement indicators). See also: Engineering geology; Rock mechanics; Soil mechanics

The process by which seriously disturbed land surfaces are stabilized against the hazards of water and wind erosion. All seriously disturbed land areas are in need of reclamation and should be stabilized and reclaimed as quickly as possible after disturbance. Disturbance comes from major construction projects such as interstate highway systems, shopping centers, and housing developments, and from surface mining operations for coal, stone, gravel (see illustration), gold, phosphate, iron, uranium, and clay. Surface mining for coal is responsible for almost one-half of the total land area disturbed in the United States, another one-fourth is from sand and gravel, and the remainder is from mining of other materials and construction. See also: Erosion

The removal of a soluble fraction, in the form of a solution, from an insoluble, permeable solid with which it is associated. The separation usually involves selective dissolving, with or without diffusion, but in the extreme case of simple washing it consists merely of the displacement (with some mixing) of one interstitial liquid by another with which it is miscible. The soluble constituent may be solid (as the metal leached from ore) or liquid (as the oil leached from soybeans).

The process of exploring the deep seabed and recovering minerals from seawater and from deposits on and under the seabed. While the world's demand for mineral commodities is increasing at a rapid rate, most of the developed countries have been thoroughly explored for surface outcroppings of mineral deposits. Advances in oceanography and mining have highlighted the importance of the ocean as a source of minerals and indicated that the technology required for their exploitation is in some cases already available (Fig. 1).

A deposit of material in Earth's crust that is of economic interest and that is presently recoverable or may be recoverable in the future. A mineral resource includes the entire commodity that exists; a mineral reserve represents that fraction of a commodity that can be recovered economically. Many items that are produced, used, or consumed in modern society—for example, computers, electronic equipment, glasses, motor vehicles, and jewelry—contain or include mineral resources that have to be obtained through extraction from the ground (see figure). See also: Earth's crust

The removal of minerals, metals, hydrocarbons, and other geological materials from Earth, including production from surface waters and from wells. Mining is an ancient human activity originally involving rocks, such as flint, along with readily available metals for making weapons and tools. Usually the oil and gas industries are regarded as separate from the mining industry and will not be covered in-depth in this article (see the "Petroleum engineering" article for more information). As a term, "mining industry" commonly includes such functions as exploration, mineral separation, hydrometallurgy, electrolytic reduction, and smelting and refining, even though these functions are not actually mining operations. See also: Hydrometallurgy; Metallurgy; Mineral; Mineral resource; Rock