Mining
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This article is about mineral extraction. "Mining" can also refer to installing explosive devices. See Mine for other meanings, or Mining, Upper Austria for the village in Austria.
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, copper, gold, silver, diamonds, iron, precious metals, lead, limestone, nickel, phosphate, oil shale, rock salt, tin, uranium, and molybdenum. Any material that cannot be grown from agricultural processes must be mined. Mining in a wider sense can also include extraction of petroleum, natural gas, and even water.
[edit] History
The oldest known mine in the archaeological record is the "Lion Cave" in Swaziland. At this site, which by radiocarbon dating is 43,000 years old, paleolithic humans mined for the iron-containing mineral hematite, which they ground to produce the red pigment ochre. Sites of a similar age where Neanderthals may have mined flint for weapons and tools have been found in Hungary.
Ancient Egyptians operated malachite mines at Wady Maghareh on the Sinai Peninsula and at Timna in the Negev. At first, the bright green stones were used for ornamentation and for pottery glaze, but approximately 1,200 BCE, Egyptians discovered that malachite could be converted into copper by the application of intense heat and air.
In North America there are ancient, prehistoric copper mines along Lake Superior that were part of an extensive native trade network of copper tools, points, arrowheads, and artifacts. Some copper points that were found are over 3000 to 4000 years old, and copper was traded throughtout the continent along major river routes. In addition, quartz, flint, and other minerals were are also mined, worked, and traded. In Manitoba there are ancient quartz mines in the north, and in Southeastern Manitoba by the Winnipeg River in Whiteshell Provincial Park.
Turquoise was mined in pre-Columbian America in the Cerillos Mining District in New Mexico, where a mass of rock 200 feet (60 m) in depth and 300 feet (90 m) in width was removed with stone tools; the mine dump covers 20 acres (81,000 m²). Black gun powder in mining was first used in a mineshaft under Banská Štiavnica, Slovakia in 1627, in the same town in 1762 the first Mining Academy in the world was established.
Mining in the United States became prevalent in the 19th century. Mining for minerals and precious metals, such as in 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 time period many white Americans and post-slavery African Americans, with the aid of railroads, travelled west for work opportunities in mining. Many western cities such as Denver and Sacramento originated as mining towns.
[edit] Steps in the mining process
- Prospecting to locate ore
- Exploration to find and then define the extent and value of ore where it is located ("ore body")
- Conduct resource estimate to mathematically estimate the extent and grade of the deposit
- Conduct mine planning to evaluate the economically recoverable portion of the deposit (and including reclamation planning)
- Conduct a feasibility study to evaluate the total project and make a decision as whether to develop or walk away from a proposed mine project. This includes a cradle to grave analysis of the possible mine, from the initial excavation all the way through to reclamation.
- Development to create access to an ore body
- Exploitation to extract ore on a large scale
- Reclamation to make land where a mine had been suitable for future use
[edit] Mining techniques
Mining techniques can be divided into two basic excavation types:
Solution mining is a particular mining technique that is used to mine minerals (potash, potassium chloride, sodium chloride, sodium sulphate) which dissolve in water.
[edit] Extractive metallurgy
The science of extractive metallurgy is a specialized area in the science of metallurgy that studies the extraction of valuable metals and minerals from their ores, especially through 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 (extractive metallurgy) of valuable metals or minerals from their gangue (waste material).
- See also: biomineralization
[edit] Environmental effects and mitigation
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 take careful measures to mitigate any type of water contamination that could be caused by mines. In modern American 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.
[edit] Mining industry
While exploration and mining can sometimes be conducted by individual entrepreneurs or small business, most modern-day mines are large enterprises requiring large amounts of capital to establish. Consequently, the mining sector of the industry is dominated by large, often multinational, mostly publicly-listed companies. See Category:Mining companies for a list. However, what is referred to as the 'mining industry' is actually two sectors, one specializing in exploration for new resources, the other specializing in mining those resources. The exploration sector is typically made up of individuals and small mineral resource companies dependant on public investment. The mining sector is typically large and multi-national companies sustained by mineral production from their mining operations.
[edit] 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 Survey 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.
[edit] Mine planning software
One of the most dramatic changes in the mining industry has been the role that sophisticated three-dimensional mine planning software packages have had. Once the decision has been taken to proceed with a mine, one will need to create detailed designs that take into account the topography and infrastructure and of course, the physical parameters of the orebody. Manual design and old fashioned planning methods can be tedious and there are many road blocks that were unique depending on the nature of the mine (e.g., panel layouts, stope designs, decline design, ramp design). Initially with the 3-D technology relatively simple tasks - like rendering graphic images of drill holes - meant that it became easier for surveyors, geologists, mine planners, mining engineers and other technical staff to manipulate and visualize data. In recent years the range of integrated mine planning tools have meant that massively complex models can be built to optimize the extraction and processing of mineral resources.
Mining Software Links
- Datamine Datamine
- Gemcom Gemcom
- Mincom MinCom
- Mintec MineSight
- Surpac Surpac
- Maptek Vulcan3D
- Whittle Whittle
- Micromine Micromine
[edit] 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 causes exposure to harmful gases, heat and dust inside sub-surface mines. These can cause harmful physiological effects or death. Methane gas is a common source of ignition of explosions in coal mines and can propagate into the more violent coal dust explosions. High temperatures and humidity may result in any of the heat illnesses including heat stroke which can be fatal. Dusts can cause lung problems. These include silicosis, asbestosis and pneumoconiosis also known as miners lung or black lung disease.
A ventilation system is set up to course air through the working areas of the mine. The air movement necessary for effective mine ventilation is generated by one or more large mine fans usually located above ground. In the United States, main fans at coal mines are required to be above ground. Air flows in one direction only, making circuits through the mine such that each main work area receives a supply of fresh air.
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:
- A death of an individual at a mine;
- An injury to an individual at a mine which has a reasonable potential to cause death;
- An entrapment of an individual for more than thirty minutes;
- An unplanned inundation of a mine by a liquid or gas;
- An unplanned ignition or explosion of gas or dust;
- An unplanned mine fire not extinguished within 30 minutes of discovery;
- An unplanned ignition or explosion of a blasting agent or an explosive;
- 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;
- A coal or rock outburst that causes withdrawal of miners or which disrupts regular mining activity for more than one hour;
- 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;
- 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
- 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.
[edit] 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, like continuous mining, 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, Eimco Elecon India Limited.
[edit] Abandoned mines
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. Old mine workings, caves, etc are commonly hazardous simply due to the lack of oxygen in the air and this is a deadly killer which provides no warning to those entering such an environment.
Every year, dozens of people are injured or killed in recreational accidents on mine property. It is only fair to note, however, that the majority of these deaths are not related to mine exploration. Drownings in open quarries and ATV accidents on abandoned mine properties are the main culprits behind these deaths. 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.
[edit] See also
- Acid mine drainage
- Coal mining
- Comstock Lode
- Gold mining
- National Mining Hall of Fame
- Remediation
- Ore grade
- Office of Surface Mining- United States Mining Regulation Agency
- TauTona- The deepest mine in the world
- Mines rescue
- General Mining Act of 1872
- Mining engineering
[edit] References
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Wikimedia Commons has media related to: |
- Bhattacharya Jayanta (2003) Principles of Mine Planning, Allied Publishers, New Delhi, India. 454 pages
- Morrison, Tom (1992) Hardrock Gold: A Miner's Tale (ISBN 0-8061-2442-3)
- Geobacter Project: Gold mines may owe their origins to bacteria (in PDF format)
[edit] External links
- Mining Technology Mining, quarrying and tunnelling industry news, projects, suppliers and glossary.
- MBendi World Mining Overview, including detailed reports by commodity, operator and geographical area
- National Mining Association
- Northeastern Mine Research Abandoned mine research and history.
- Western Mining History Mining in the American West.
- Western Museum of Mining and Industry
- The Society for Mining, metallurgy and Exploration SME-AIME
- The Australasian Institute of Mining and Metallurgy The AusIMM
- Mining the Environment and Indigenous Development
- Photographic Essays of New Jersey's Abandoned Mines
- Mining in Vermont
