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mining,extraction of solid mineral resources from the earth. These resources include ores, which contain commercially valuable amounts of metals, such as iron and aluminum; precious stones, such as diamonds; building stones, such as granite; and solid fuels, such as coal and oil shale. The search for and discovery of mineral deposits is called prospectingprospecting,
search for mineral deposits suitable for mining. Modern prospecting has replaced earlier methods based on chance or superstition (e.g., use of the divining rod) with others based on a scientific knowledge of modern geology and mineralogy.
..... Click the link for more information. , or exploration. When a mineral deposit is found, it is studied to determine if it can be mined profitably. If so, the deposit can be worked or extracted by a variety of mining methods.
Surface Mining Methods
Strip mining (see coal miningcoal mining,
physical extraction of coal resources to yield coal; also, the business of exploring for, developing, mining, and transporting coal in any form. Strip mining is the process in which the overburden (earth and rock material overlying the coal) is removed to expose a
..... Click the link for more information. ), open-pit (or open-cut) mining, and quarryingquarrying,
open, or surface, excavation of rock used for various purposes, including construction, ornamentation, road building, and as an industrial raw material. Rock that has been quarried is commonly called stone.
..... Click the link for more information. are the most common mining methods that start from the earth's surface and maintain exposure to the surface throughout the extraction period. The excavation usually has stepped, or benched, side slopes and can reach depths as low as 1,500 ft (460 m). In strip mining, the soft overburden, or waste soil, overlying the ore or coal is easily removed. In open-pit mining the barren rock material over the ore body normally requires drilling and blasting to break it up for removal. A typical mining cycle consists of drilling holes into the rock in a pattern, loading the holes with explosives, or blasting agents, and blasting the rock in order to break it into a size suitable for loading and hauling to the mill, concentrator, or treatment plant. There the metals or other desired substances are extracted from the rocks (see metallurgymetallurgy
, science and technology of metals and their alloys. Modern metallurgical research is concerned with the preparation of radioactive metals, with obtaining metals economically from low-grade ores, with obtaining and refining rare metals hitherto not used, and with the
..... Click the link for more information. ).
Underground Mining Methods
Under certain circumstances surface mining can become prohibitively expensive and underground mining may be considered. A major factor in the decision to operate by underground mining rather than surface mining is the strip ratio, or the number of units of waste material in a surface mine that must be removed in order to extract one unit of ore. Once this ratio becomes large, surface mining is no longer attractive. The objective of underground mining is to extract the ore below the surface of the earth safely, economically, and with as little waste as possible. The entry from the surface to an underground mine may be through an adit, or horizontal tunnel, a shaft (see shaft sinkingshaft sinking,
excavation from the surface of an opening in the earth. Shafts, which are generally vertical, are usually distinguished from tunnels, which are horizontal. Little difficulty is experienced in shaft sinking through solid rock, which contains little water.
..... Click the link for more information. ), or vertical tunnel, or a declined shaft. A typical underground mine has a number of roughly horizontal levels at various depths below the surface, and these spread out from the access to the surface. Ore is mined in stopes, or rooms. Material left in place to support the ceiling is called a pillar and can sometimes be recovered afterward. A vertical internal connection between two levels of a mine is called a winze if it was made by driving downward and a raise if it was made by driving upward.
A modern underground mine is a highly mechanized operation requiring little work with pick and shovel. Rubber-tired vehicles, rail haulage, and multiple drill units are commonplace. In order to protect miners and their equipment much attention is paid to mine safety. Mine ventilation provides fresh air underground and at the same time removes noxious gases as well as dangerous dusts that might cause lung disease, e.g., silicosissilicosis
, occupational disease of the lungs caused by inhalation of free silica (quartz) dust over a prolonged period of time. Free silica is dispersed in the air and inhaled by workers engaged in the mining of lead, hard coal, and gold, in cutting sandstone and granite, in
..... Click the link for more information. . Roof support is accomplished with timber, concrete, or steel supports or, most commonly, with roof bolts, which are long steel rods used to bind the exposed roof surface to the rock behind it.
Although surface and underground mining are the most common techniques, there are a number of other mining methods. In solution mining the valuable mineral is brought into a liquid solution by some chemical or bacteria. The resultant liquid is pumped to the surface, where the mineral or metal is taken out of solution by precipitationprecipitation,
in chemistry, a process in which a solid is separated from a suspension, sol, or solution. In a suspension such as sand in water the solid spontaneously precipitates (settles out) on standing. In a sol the particles are precipitated by coagulation.
..... Click the link for more information. or by ion exchange (e.g., the Frasch processFrasch process
[for Herman Frasch, the German-American chemist who devised it], process for the extraction of sulfur from subsurface deposits. Three pipes, one inside another, are sunk to the bottom of the sulfur bed.
..... Click the link for more information. ). In glory-hole mining a steep-sided, funnel-shaped surface excavation is connected to tunnels below it. Rocks blasted off the sides of the excavation fall into the tunnels, from which they are then removed. Gopher mining is an old-fashioned method still used in very small mines. Narrow, small holes are driven in order to extract the ore (e.g., gold) as cheaply as possible. In placer mining no excavation is involved; instead, gravel, sand, or talus (rock debris) is removed from deposits by hand, hydraulic nozzles, or dredging. The ore is separated from the waste by panning or sluicing.
Environmental and Legal Concerns
Associated with mining are many environmental concerns. Large-scale excavation is often necessary to extract a small amount of ore. Ore extraction disrupts the topsoil and can displace local animals and plants, and sometimes native human populations. Runoff can contaminate nearby water sources with pollutants such as the mercury and sodium cyanide used in gold mining. Waste materials and smelters can cause sulfurous dust clouds that result in acid rain. Abandoned strip mines have often been used as unregulated landfills for hazardous wastes. Several pieces of legislation in the United States, the Surface Mining Control and Reclamation Act (1977) and the Comprehensive Environmental Response, Compensation, and Liability Act, or Superfund Act (1986), address these issues, but enforcement has been difficult.
Another act that affects mining in the United States is the 1872 Mining Act. This now controversial act, which was originally designed to encourage settlement of the West, allows mining companies to purchase land for $2.50 per acre. In the late 20th cent., despite many efforts at reform, the law and the $2.50 per acre price still stood, despite the fact that the ore contained in the land could be worth billions of dollars.
See R. Peele and J. A. Church, ed., Mining Engineer's Handbook (3d ed.; 2 vol., 1941); R. S. Lewis and G. B. Clark, Elements of Mining (3d ed. 1964); E. Pfleider, ed., Surface Mining (1968); G. C. Amstutz, Glossary of Mining Geology (1971); C. Gregory, A Concise History of Mining (1981); M. K. Tolba (United Nations Environment Programme), Saving Our Planet (1991); A. Warhurst, Environmental Degradation from Mining and Mineral Processing in Developing Countries (1994).
the branches of science and technology that embrace the processes of extracting minerals from the interior of the earth.
For thousands of years mining was limited to the extraction of only solid minerals (nonmetallic construction materials, ore, and so on). The extraction of petroleum began in the second half of the 19th century; that of natural gas, in the early 20th century.
The extraction of minerals is preceded by prospecting, which is necessary to determine the reserves, ore quality, and economic feasibility of exploiting a given deposit, the production capacity of a mining enterprise, and the methods of working deposits. Geophysical prospecting methods are being used more widely; geochemical and microbiological prospecting methods are in the process of further development. The results of prospecting surveys and stereogeomet-ric measurements are represented on maps, plans, sections, and charts by means of mining-surveying and geometric methods.
When sufficient mineral reserves have been discovered and the technical and economic feasibility of exploiting them has been shown, development of the deposit is begun on the basis of a preliminary plan. This is done by drilling holes or excavating a network of underground or opencut mines according to a specific plan; the necessary surface and subsurface facilities are constructed for stripping the deposit.
Industrial shaft operation specifications require a minimum of two exits from underground mines to the earth’s surface: one for the fresh air supply, and the other for exhaust air. These exits are usually the openings to the deposit and the network of interconnected workings, such as vertical or sloping mine shafts and tunnels. The depth of vertical shafts may exceed 2,000 m in some cases. The methods of sinking shafts and other mine workings depends on the nature and degree of flooding of the rock through which they are cut. To prevent collapses, mine walls are braced in proportion to the amount of rock excavated.
After the deposit has been stripped, so-called development is begun on the mineral with the purpose of preparing the deposit for the cleaning work. Upon completion of the development work, the cleaning work is begun in order to extract the mineral. The faces for performing the cleaning work are called the working faces, and the resulting workings are called excavations. The temporal and spatial procedure of the development and cleaning work, which is established for specific natural, geologic, technical, and economic conditions, is called the system of working the deposit.
The preliminary excavations and the cleaning work for the extraction of the minerals are usually performed by drilling, rock-loading, and cutting-loading machines.
The extracted mineral is delivered from the working face to the earth’s surface by means of a mine conveyor system; loads and personnel are transported along the mine shaft by a mine hoist.
All underground mines are supplied with fresh air. Stationary electric lighting is installed in the underground workings, and the workers are furnished with portable miner’s lamps. The water that accumulates in underground workings is continually removed by a drainage system. Special services monitor the regularity and safety of underground operations, and measures are taken to prevent and extinguish fires and to cope with accidents and their consequences.
Mining had its beginnings at an early stage in the development of human society. During the period of the tribal system underground mines, sometimes supported by wood, were excavated for the extraction of silicon. Stone implements and picks made from antlers were used for mining. The systematic mining of copper and tin ores and the extraction of gold and silver began in slaveowning society. Remains of ancient mines from the Bronze Age have been discovered on the territory of the USSR. Mine workings with traces of supports and ladders from the same period have survived in Central Europe. Mining existed in China, Japan, and regions of the American continent long before the Common Era.
The mastery of the production of iron became the main factor in the development of the productive forces in ancient society. The mines exploited the labor of huge numbers of slaves and convicts. Mining played an important role in the economy of ancient Rome toward the end of the Republic era and during the Empire period (first century B.C. to the third century A.D.).
Significant progress was made in mining with the development of feudal relations. In the 11th to 13th centuries extensive developments began to take place in mining in Central Europe, although rocks were still drilled by hand. Important improvements were made in mining in Europe during the 15th and 16th centuries. The use of the horse drive and the waterwheel for mine hoisting and drainage devices permitted mining operations down to a depth of 150 m. Blasting operations appeared and began to replace the firing method of demolition. Wet ore concentration was introduced, making possible the mining of relatively low-grade ores. In 1512 a charter for a wet stamp mill was granted in Saxony. Timber flooring for the movement of carts loaded with minerals was first installed during that period. The first mining schools were established, and manuals on mining appeared (On Mining and Metallurgy by G. Agricola, 1556). Steam engines, which were used first for pumping water (the Englishman T. Newcomen in 1711–12) and later for mine hoisting, found application in mining earlier than in other industries.
The changeover to the large-scale use of machinery in mining was accomplished in the period of the industrial revolution (late 18th to early 19th century). In 1815 the Englishman H. Davy invented a safe miner’s lamp. Drilling technology was improved, explosives were used more and more widely, and horse-drawn rail hauling was introduced. Steel cables for mine hoisting and hauling were first used in the 1830’s. The first efficient coal-cutting machines appeared in the mid-1850’s.
The conditions for the development of mining underwent a change once again between the late 19th and early 20th centuries because of a huge increase in the demand for minerals. The technology of sinking mine shafts developed intensively. Improved sinking, ventilating, and drainage methods allowed mining depths to be extended to 1,000 m and sometimes to 2,000 m. Highly efficient systems were created for mining coal and ore deposits. Electric drive was introduced for hoisting machinery, pumps, and ventilators, mine transportation was electrified, cutting was mechanized by means of coal-cutting machines, and pick-hammers operated by compressed air were widely adopted. Independent scientific and technical disciplines emerged that were concerned with questions related to the extraction of separate types of minerals, such as coal, ores, petroleum, and peat.
The major challenges confronting mining in the USSR are the rational use of mineral resources, significant increases in economic efficiency, and the improvement of working conditions (mining is the most difficult and dangerous area of the large-scale use of labor). Intensive searches are underway for new systems of mining deposits, more powerful mechanical equipment, the use of automation, and the construction of an extraction technology based on flow production. The mechanization of the breaking and loading of coal continues to increase; the loading of coal and rock in development workings is performed by cutting-loading and loading machines. Breaking and loading during the extraction of ore is also being mechanized. The use of automation and remote control of machines and equipment is expanding gradually. The mining industry is adopting the use of metal supports (in place of wood supports) and movable powered supports. There is a marked tendency to reduce in every possible way the disconnectedness of mining operations and to speed up excavation in a relatively limited number of faces. In view of this, high-output mines are being put into operation.
Increased mining efficiency is achieved primarily by the wider adoption of opencut deposit mining methods. With the opencut mining method, labor productivity is 7–10 times higher than that of underground mines, and the prime cost of extraction is considerably lower. Extraction by the opencut method increased sharply in the coal industry during the second half of the 1950’s. The relative proportion of quarry-extracted coal rose from 6 percent to 30 percent in the total world balance over the period from 1913 to 1968. In the USSR, 25 percent of the coal extracted in 1968 came from quarries.
In the USSR (1969) the opencut mining method accounted for 77 percent of the iron ore, 64 percent of nonferrous metal ores, 56.4 percent of the manganese, 46.6 percent of mining chemicals, and 100 percent of nonmetallic minerals and construction materials.
A great deal of progress has been made in the study of the physical properties of rocks, making it possible to arrive at the optimal solutions in the design and construction of rock-crushing machinery and tools, as well as in mineral recovery methods.
Theoretical and experimental work is continuing in various areas of mining that offer the possibility of the subterranean extraction of minerals without the use of human labor (by geotechnological methods), as well as the extraction of minerals from the ocean floor.
The extraction of liquid and gaseous minerals, which accounted for approximately 60 percent of the USSR’s fuel balance in 1969, has increased immeasurably, especially during the period from 1960 to 1970. The development of the extraction of these minerals was closely associated with the development of well-drilling technology. The exploitation of petroleum deposits is conducted at great depths in the sea by artificial action on the stratum (for example, by flooding). The gas industry of the USSR is creating efficient gas fields with annual outputs of 75–100 billion cu m and large-diameter main gas pipelines.
REFERENCESBokii, B. V. Gornoe delo, 3rd ed. Moscow, 1959.
Sheviakov, L. D. Razrabotka mestorozhdenii poleznykh iskopaemykh, 4th ed. Moscow, 1963.
Agoshkov, M. I., and G. M. Malakhov. Podzemnaia razrabotka rudnykh mestorozhdenii. Moscow, 1966.
Mel’nikov, N. V. Mineral’noe toplivo, 2nd ed. Moscow, 1971.
Rzhevskii, V. V. Tekhnoiogiia i kompleksnaia mekhanizatsiia otkrytykh gornykh rabot. Moscow, 1968.
Tekhnoiogiia podzemnoi razrabotki plastovykh mestorozhdenii poleznykh iskopaemykh. Moscow, 1969.
N. V. MEL’NIKOV
The taking of minerals from the earth, including production from surface waters and from wells. Usually the oil and gas industries are regarded as separate from the mining industry. The term mining industry commonly includes such functions as exploration, mineral separation, hydrometallurgy, electrolytic reduction, and smelting and refining, even though these are not actually mining operations. See Hydrometallurgy, Metallurgy, Ore dressing
Mining is broadly divided into three basic methods: opencast, underground, and fluid mining. Opencast mining is done either from pits or gouged-out slopes or by surface mining, which involves extraction from a series of successive parallel trenches. Dredging is a type of surface mining, with digging done from barges. Hydraulic mining uses jets of water to excavate material.
Underground mining involves extraction from beneath the surface, from depths as great as 10,000 ft (3 km), by any of several methods.
Fluid mining is extraction from natural brines, lakes, oceans, or underground waters; from solutions made by dissolving underground materials and pumping to the surface; from underground oil or gas pools; by melting underground material with hot water and pumping to the surface; or by driving material from well to well by gas drive, water drive, or combustion. Most fluid mining is done by wells. In one experimental type of well mining, insoluble material is washed loose by underground jets and the slurry is pumped to the surface. See Petroleum engineering
The activities of the mining industry begin with exploration, which, since accidental discoveries or surficially exposed deposits are no longer sufficient, has become a complicated, expensive, and highly technical task. After suitable deposits have been found and their worth proved, development, or preparation for mining, is necessary. For opencast mining, this involves stripping off overburden; and for underground mining, the sinking of shafts, driving of adits and various other underground openings, and providing for drainage and ventilation. For mining by wells, drilling must be done. For all these cases, equipment must be provided for such purposes as blasthole drilling, blasting, loading, transporting, hoisting, power transmission, pumping, ventilation, storage, or casing and connecting wells. Mines may ship their crude products directly to reduction plants, refiners, or consumers, but commonly, concentrating mills are provided to separate useful from useless (gangue) minerals.
A unique feature of mining is the circumstance that mineral deposits undergoing extraction are “wasting assets,” meaning that they are not renewable as are other natural resources. This depletability of mineral deposits requires that mining companies must periodically find new deposits and constantly improve their technology in order to stay in business. Depletion means that the supplies of any particular mineral, except those derived from oceanic brine, must be drawn from ever-lower-grade sources.