Difference between revisions of "Mining" - New World Encyclopedia

From New World Encyclopedia
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:*[[Shaft mining]]*: This method involves the drilling of a mine shaft that is a vertical (or steeply inclined) passageway to an underground mine. Horizontal projections (called "drifts" or "galleries") are dug from the central shaft. The workers, equipment, and minerals are raised and lowered by a "cage" operated through the central shaft.
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:*[[Shaft mining]]*: This method involves drilling one or more mine shafts that are vertical (or steeply inclined) passageways to an underground mine. Horizontal projections (called "drifts" or "galleries") are dug from the shaft. The workers, equipment, and minerals are raised and lowered by a "cage" operated through the shaft.
  
  
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The [[horizontal]] [[working]]s extending from the central shaft are called ''drifts'', ''galleries'' or ''levels''. This is contrasted to: [[Drift mining]]
 
The [[horizontal]] [[working]]s extending from the central shaft are called ''drifts'', ''galleries'' or ''levels''. This is contrasted to: [[Drift mining]]
  
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:*[[Hard rock mining]]*: This term is used for various techniques to mine ore bodies by creating underground "rooms" or ''stopes'' supported by pillars of standing rock. The ore is accessed by drilling a decline (spiral tunnel) or vertical shaft. Often a mine has a decline for personnel and machinery access, and a shaft for ore haulage.
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Hard rock mining is used for mining many ore types, including [[gold]], [[copper]], [[zinc]], [[lead]], and [[diamond]]s.
  
  
:*[[Hard rock mining]]*
 
 
:*[[Borehole mining]]*
 
:*[[Borehole mining]]*
  

Revision as of 18:57, 4 August 2006

Chuquicamata, the largest open pit copper mine in the world, Chile

Mining is the extraction of valuable minerals or other geological materials from the earth, usually (but not always) from an ore body, vein, or (coal) seam. Materials recovered by mining include bauxite, coal, diamonds, iron, precious metals, lead, limestone, nickel, phosphate, rock salt, tin, uranium, and molybdenum. In a broader sense, the term "mining" may also be applied to the extraction of petroleum, natural gas, and even water.

History

Miners at the Tamarack mine in Copper Country, Michigan, in 1905.

The oldest known mine in the archaeological record is "Lion Cave" in Swaziland. Radiocarbon dating indicates that this site is 43,000 years old. It is thought that paleolithic humans may have mined the area for the iron-containing mineral hematite, which they ground to produce the red pigment ochre. Sites of similar age have been found in Hungary, where Neanderthals may have mined flint for weapons and tools.

Another early mining operation was the turquoise mine operated by ancient Egyptians at Wady Maghareh on the Sinai peninsula. Turquoise was also mined in pre-Columbian America, in the Cerillos mining district in New Mexico, where a mass of rock 200 feet (60 meters (m)) deep and 300 feet (90 m) wide was removed with stone tools. the mine dump covers 20 acres (81,000 m²). The first use of black gun powder for mining appears to have been in a mineshaft under Banská Štiavnica, Slovakia, in 1627. The first mining academy in the world was established in the same town in 1762.

Mining in the United States became prevalent in the nineteenth century. Mining for minerals and precious metals, such as during the California gold rush in the mid 1800s, was very important in westward expansion to the Pacific coast, along with ranching and exploration of oil and gas fields. During this period, many Americans (both Caucasian and African American) traveled west by railroad for work opportunities in mining. Western cities such as Denver, Colorado, and Sacramento, California, originated as mining towns.

Planning a mining project

Several steps need to be taken before a mining project can begin.

  1. Prospecting, to discover the locations of ore.
  2. Exploration, to defining the extent and value of the ore that was located.
  3. Resource estimation, to mathematically estimate the extent and grade of the deposit.
  4. Mine planning, to evaluate the economically recoverable portion of the deposit.
  5. Conducting a feasibility study, to evaluate the total project and to decide whether or not to proceed with the project. It includes a cradle-to-grave analysis of the possible mine, from initial excavation all the way through land reclamation.

Once the decision has been made to start the project, an infrastructure has to be put in place to create access to the ore body. When that is completed, the land is excavated and the ore is extracted on a large scale. Finally, a well-planned mining project ends with reclamation efforts to make the land suitable for future use.

Mine planning software

One of the most dramatic changes in the mining industry has been the role of sophisticated, three-dimensional mine planning software packages. Once the decision has been taken to proceed with a mine, one needs to create detailed designs that take into account the area's topography and infrastructure, as well as the physical parameters of the ore body. Manual design and old-fashioned planning methods can be tedious and have to deal with many unique challenges that depend on the nature of the mine. Initially, the 3-D software was used for relatively simple tasks, such as rendering graphic images of drill holes. That made it easier for surveyors, geologists, mine planners, mining engineers, and other technical staff to manipulate and visualize data. In recent years, however, a wide range of integrated mine planning tools have been developed, so that massively complex models can be built to optimize the extraction and processing of mineral resources.

Mining techniques

There are two basic approaches for mining ore: surface mining, for the extraction of ores that are near the Earth's surface; and subsurface mining (or underground mining), for the extraction of ores that lie underground. Each of these can be performed by one of several techniques.

1. Surface mining

  • Open-pit (or open-cast) mining: It is a method of extracting rock or minerals from an open pit (or "borrow"). The mine is dug on "benches" (at 3-meter or 6-meter levels), corresponding to horizontal levels of the mine. Most walls of the pit are dug at an angle less than vertical and are stepped, to minimize the danger of falling rock.
  • Quarrying: A quarry is a type of open-pit mine, but the term is generally used for extracting building materials, such as dimension stone. Quarries rarely use benches as they are usually shallower than other types of open-pit mines.
  • Strip mining: Similar to open-pit mining, strip mining involves removal of soil and rock (overburden) that overlies the ore.
  • Placer mining (pronounced "plass-er" mining): It involves the use of water, usually under pressure, to move and separate the valuable material from soil and rock in the deposit. Placer mining became famous in North America during the California and Klondike gold rushes.
  • Mountaintop removal: This process, used for coal mining, involves massive restructuring of the land to gain access to a deposit that may lie as much as 1,000 feet beneath the surface. The mountain (or overburden) is clear-cut, leveled with explosives, and pushed into a nearby valley or hollow to expose the underlying coal.

2. Subsurface mining

  • Drift mining: It involves accessing the desired material by making an approximately horizontal cut into a side of the earth, such as a hillside. The drift (or cut) may have a slight incline to aid in removing the material.
  • Slope mining: In this method, a shaft is dug at a downward slope to access the material desired, such as coal.


  • Shaft mining: This method involves drilling one or more mine shafts that are vertical (or steeply inclined) passageways to an underground mine. Horizontal projections (called "drifts" or "galleries") are dug from the shaft. The workers, equipment, and minerals are raised and lowered by a "cage" operated through the shaft.


Shaft mining is a type of underground mining done by use of a mine shaft.

A mine shaft is a vertical or inclined passageway used to access to an underground mining facility. On the surface above the shaft stands a building known as the pit head (or poppet head), which historically contained a winding engine and in modern times contains an electric hoist controller. This raises and lowers the cage within the shaft. The cage serves as a lift for the transportation of minerals, equipment and workers.

The horizontal workings extending from the central shaft are called drifts, galleries or levels. This is contrasted to: Drift mining


  • Hard rock mining: This term is used for various techniques to mine ore bodies by creating underground "rooms" or stopes supported by pillars of standing rock. The ore is accessed by drilling a decline (spiral tunnel) or vertical shaft. Often a mine has a decline for personnel and machinery access, and a shaft for ore haulage.

Hard rock mining is used for mining many ore types, including gold, copper, zinc, lead, and diamonds.


  • Borehole mining

Extractive metallurgy

Extractive metallurgy is a specialized area in the science of metallurgy. It studies the extraction of valuable metals and minerals from their ores, especially by chemical or mechanical means. Mineral processing (or mineral dressing) is a specialized area in the science of metallurgy that studies the mechanical means of crushing, grinding, and washing that enable the separation of valuable metals or minerals from their gangue (waste material).

Environmental effects and mitigation

Iron hydroxide precipitate stains a stream receiving acid drainage from surface coal mining.

Environmental issues can include erosion, formation of sinkholes, loss of biodiversity, and contamination of groundwaters by chemicals from the mining process and products.

Modern mining companies in many countries are required to follow strict environmental and rehabilitation codes, ensuring the area mined is returned to close to its original state, or an even better environmental state than before mining took place. In some countries with pristine environments, such as large parts of Australia, this is impossible despite the best intentions. Past mining methods have had, and methods used in countries with lax environmental regulations can continue to have, devastating environmental and public health effects.

Mining can have adverse effect on surrounding surface and ground water if protection measures are not exercised. The result can be unnaturally high concentrations of some chemical elements over a significantly large area of surface or subsurface. Coal mining releases approximately twenty toxic release chemicals, of which 85% is said to be managed on site. Combined with the effects of water and the new 'channels' created for water to travel through, collect in, and contact with these chemicals, a situation is created where mass-scale contamination can occur. In well-regulated mines hydrologists and geologists to careful measures to mitigate any type of water contamination that could be caused by mines. In modern mining, operations must, under federal and state law, meet standards for protecting surface and ground waters from contamination, including acid mine drainage (AMD). To mitigate these problems water is continuously monitored at coal mines. The five principal technologies used to control water flow at mine sites are: diversion systems, containment ponds, groundwater pumping systems, subsurface drainage systems, and subsurface barriers. In the case of AMD, contaminated water is generally pumped to a treatment facility that neutralizes the contaminants.

Some examples of environmental problems associated with mining operations are:

Ashio Copper Mine, Ashio, Japan was the site of substantial pollution at end of the nineteenth century
Berkeley Lake, an abandoned pit mine in Butte, Montana that has filled with water which is now acidic and poisonous. In 2003, a water treatment plant came on-line, initially treating "new" water entering the pit and thereby reducing the rate of rise of pit water. Treated water is currently used in the concentrator of the nearby Montana Resources Continental Pit, but it is clean enough to return to Silver Bow Creek. Eventually, water in the pit itself will be treated.
Britannia Mines, a former copper mine near Vancouver, British Columbia. Copper from the abandoned mine washes into Howe Sound, polluting the water. No animal life remains there now. - Latest reports are that after a water treatment plant was put in, fish are returning to Britannia Bay - maybe for the first time ever. The name used by the First Nations tribes of Britannia Beach, even before mining started, means "The Place of No Fish".
Scouriotissa, a copper mine in Cyprus that has been abandoned. Contaminated dust blows off this site.
Tar Creek, an abandoned mining area in Picher, Oklahoma that is now an Environmental Protection Agency superfund site. Water in the mine has leaked through into local groundwater, contaminating it with metals such as lead and cadmium. [1]

Although such issues have been associated with some mining operations in the past, modern mining practices have improved significantly and are subject to close environmental scrutiny. To ensure completion of reclamation (restoring mine land) the Office of Surface Mining requires that mining companies post a bond to be held in escrow until productivity of reclaimed land has been convincingly demonstrated. Since 1978 the mining industry has reclaimed more than 2 million acres (8,000 km²) of land. This reclaimed land has renewed vegetation and wildlife in previous mining lands and can even be used for farming and ranching.

For further reading on reclamation of former mining sites, see Restoration ecology.

Mining industry

While exploration and mining are sometimes conducted by individual entrepreneurs and small businesses, most modern-day mines are large-scale enterprises requiring huge amounts of capital. Consequently, the industry is dominated by giant companies that are often multinational and publicly listed.

Employment in the U.S. mining industry and government regulations

Miners today do more than just dig tunnels in the Earth's subsurface. There are many different jobs, direct and indirect, in the mining industry, ranging from engineers and lab technicians to geologists and environmental specialists. Beyond employment directly linked to mine-site activity, the modern mining industry also employs many other professionals, including accountants, lawyers, sales representatives, public relations specialists, not to mention thousands of men and women involved who manufacture the machines and equipment necessary to mine minerals.

Employment in the mining industry offers highly competitive wages and benefits, especially in rural or remote areas. According to the Bureau of Labor Statistics (BLS), wages for coal miners are 30% higher than the wage earned by the average American. Employees possessing at least a bachelor's degree in mining or geological engineering can earn a median pay of over $80,000 annually.

The US Bureau of Labor Statistics estimates that 675,000 are employed in the natural resources and mining sector. Estimated employment by selected specific commodity (including mine, mill, smelter, and quarry workers) listed below is from US Geological Survery Mineral Commodity Surveys:

  • Crushed Stone - 79,700 workers
  • Copper - 7,000
  • Cement - 18,000
  • Sand and Gravel - 38,300
  • Gold - 7,600
  • Aluminum - 56,000
  • Iron Ore - 4,400
  • Platinum Group Metals - 1,600
  • Salt - 4,100
  • Phosphate Rock - 2,900

The mining industry has an experienced but aging workforce with a mean average age of 50 years and median of 46 years. Indeed, while the industry will require new employees to meet future demand, the largest dilemma currently facing mine operators is finding employees to fill vacancies left by a generation of miners, mine engineers, senior managers, technical experts and others who are set to retire between 2005 and 2015. However, the industry is struggling to meet that demand due to current low enrollment levels in mining education programs at American colleges and universities.

Mining is regulated under a comprehensive federal safety law (Federal Mine Safety and Health Act) that is administered by the Department of Labor's Mine Safety and Health Administration (MSHA). Currently under federal law, and enforced by MSHA each U.S. miner must have an approved worker training program in health and safety issues, including at least 40 hours of basic safety training for new underground miners with no experience; 24 hours for new miners at surface mines with no experience; plus eight hours of annual refresher training for all miners.


Safety issues and improvements

Safety has long been a controversial issue in the mining business especially with sub-surface mining. While mining today is substantially safer than it was in the previous decades, mining accidents and tragedies are often very high profile such as the Quecreek Mine Rescue saving 9 trapped Pennsylvania coal miners in 2002.

Mining ventilation is also seen to be a safety concern for many miners and their family. Poor ventilation of mining and exposure to harmful dust inside sub-surface mines have been known to cause lung problems called pneumoconiosis, also known as miners lung or the black lung disease. In response a ventilation system is set up to pull or push air out of the mine. The air movement necessary for effective mine ventilation is generated by a large mine fan located aboveground. The pressure differential created by the fan is great enough so that fresh air is forced in through a separate entrance. Air flows in one direction only, making a circuit through the mine.

Mining is regulated under the federal Mine Safety and Health Act by MSHA, which employs nearly one safety inspector for every four coal mines. Underground coal mines are thoroughly inspected at least four times annually by MSHA inspectors. In addition, miners can report violations, request additional inspections and cannot lose their jobs for doing so.

Immediately reportable accidents and injuries are:

  1. A death of an individual at a mine;
  2. An injury to an individual at a mine which has a reasonable potential to cause death;
  3. An entrapment of an individual for more than thirty minutes;
  4. An unplanned inundation of a mine by a liquid or gas;
  5. An unplanned ignition or explosion of gas or dust;
  6. An unplanned mine fire not extinguished within 30 minutes of discovery;
  7. An unplanned ignition or explosion of a blasting agent or an explosive;
  8. An unplanned roof fall at or above the anchorage zone in active workings where roof bolts are in use; or, an unplanned roof or rib fall in active workings that impairs ventilation or impedes passage;
  9. A coal or rock outburst that causes withdrawal of miners or which disrupts regular mining activity for more than one hour;
  10. An unstable condition at an impoundment, refuse pile, or culm bank which requires emergency action in order to prevent failure, or which causes individuals to evacuate an area; or, failure of an impoundment, refuse pile, or culm bank;
  11. Damage to hoisting equipment in a shaft or slope which endangers an individual or which interferes with use of the equipment for more than thirty minutes; and
  12. An event at a mine which causes death or bodily injury to an individual not at the mine at the time the event occurs.

Statistical analyses performed by the U.S. Department of Labor's Mine Safety and Health Administration (MSHA) show that between 1990 and 2004, the industry cut the rate of injuries (a measure comparing the rate of incidents to overall number of employees or hours worked) by more than half and fatalities by two-thirds following three prior decades of steady improvement.

Machinery

Mining machinery resembles that of other heavy industries. Heavy machinery is needed in mining to break and remove rocks of diverse hardness and toughness. Bulldozers, drills, explosives and trucks are important for digging into the land, especially in surface mining. Underground mining today tends to be more technologically sophisticated because of the dangers and expense of subsurface tunneling. Continuous mining equipment manufacturers include Joy Mining Machinery, Caterpillar, Komatsu, Volvo, Hitachi, Dynapac, Terex, Dresser, TCM, Kawasaki, Furukawa, Elphinstone, Poclain and Demag.

Abandoned Mines

Stay out of old mines! Danger sign at an old Arizona mine.

It is estimated that there are between 700,000 and 800,000 abandoned mines in the United States. Many of these abandoned mines are associated with abandoned neighboring towns often referred to as ghost towns.

Experts strongly warn against entering or exploring old or abandoned mines. It is estimated that approximately 25% of the abandoned mine lands (AML) sites pose physical safety hazards. Old mines are often dangerous and can contain deadly gases, snakes, and other dangerous animals. The entrance to an old mine in particular can be very dangerous, as weather may have eroded the earth/rock surrounding the entrance.

Every year, dozens of people are injured or killed in recreational accidents on mine property. MSHA (Mine Safety and Health Administration) launched the "Stay Out – Stay Alive" campaign in 1999. "Stay Out–Stay Alive" is a national public awareness campaign aimed at warning and educating children and adults about the dangers of exploring and playing on active and abandoned mine sites.

The Abandoned Mine Land Initiative, launched by the Western Governors Association and the National Mining Association is an effort focusing on reporting the number of high-priority AML sites, and to identify, measure and report on the progress of current reclamation cleanup programs on an annual basis.

See also

References
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External links

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