Everything about Mining totally explained
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,
magnesite,
nickel,
phosphate,
oil shale,
rock salt,
tin,
uranium and
molybdenum. Any material that can't be grown from
agricultural processes, or created
artificially in a
laboratory or
factory, is usually mined. Mining in a wider sense comprises extraction of any
non-renewable resource (for example,
petroleum,
natural gas, or even
water).
History
Since the beginning of civilization people have used
stone,
ceramics and, later,
metals found on or close to the
Earth's surface. These were used to manufacture early
tools and
weapons. For example, high quality
flint found in northern
France and southern
England were used to set
fire and break rock. Flint mines have been found in
chalk areas where seams of the stone were followed underground by shafts and galleries. The mines at
Grimes Graves are especially famous, and like most other flint mines, are
Neolithic in origin (ca 4000 BC-ca 3000 BC). Other hard rocks mined or collected for axes included the greenstone of the
Langdale axe industry based in the
English Lake District.
The oldest known mine on archaeological record is the "Lion Cave" in
Swaziland. At this site, which by
radiocarbon dating the mine dates around 4,100 BC,
paleolithic humans mined mineral
hematite, which contained
iron and was ground to produce the red
pigment ochre. Mines of a similar age in
Hungary and are believed to be sites where
Neanderthals may have mined
flint for weapons and tools.
Ancient Egyptians mined
malachite at
Maadi. At first,
Egyptians used the bright green malachite stones for ornamentations and pottery. Later, between 2,613 and 2,494 BC, large building projects required expeditions abroad to the area of Wadi Maghara in order "to secure minerals and other resources not available in Egypt itself." Quarries for
turqoise and
copper were also found at "Wadi Hamamat, Tura, Aswan and various other Nubian sites" on the
Sinai Peninsula and at
Timna.
Mining in Egypt occurred in the earliest dynasties, and the
gold mines of
Nubia were among the largest and most extensive of any in
Ancient Egypt, and are described by the Greek author
Diodorus Siculus. He mentions that
fire-setting was one method used to break down the hard rock holding the gold. One of the complexes is shown in one of earliest known maps. They crushed the ore and ground it to a fine powder before washing the powder for the
gold dust.
Europe
Mining in Europe has a very long pedigree, examples including the silver mines of
Laurium, which helped the establishment of the Greek city state, especially
Athens. However, it's the
Romans who developed large scale mining methods, especially the use of large volumes of water brought to the minehead by numerous
aqueducts. The water was used for a variety of purposes, and included using it to remove overburden and rock debris, as well as washing
comminuted or crushed ores, and driving simple machinery.
Spain was one of the most important mining regions, but all regions of the
Roman Empire were exploited. They used
reverse overshot water-wheels for dewatering their deep mines such as those at
Rio Tinto.
The
Celts, for example, who were native to
Britain, had
mined minerals for centuries, but when the
Romans came, the scale of the operations changed dramatically. The Romans needed what Britain possessed, especially
gold,
silver,
tin and
lead.
Mining in the
Medieval period is best known through the work
De Re Metallica (1556) of
Georg Agricola, who described many different mining methods then used in German or Saxon mines. Use of water power in the form of
water mills was extensive, and were employed in crushing ore, raising ore from shafts and ventilating galleries by giant
bellows.
Black powder was first used in mining in
Banská Štiavnica,
Kingdom of Hungary present-day
Slovakia in 1627. In 1762, the world's first mining academy was established in the same town.
Britain
Britain's gold mines were located in Wales at
Dolgellau and
Dolaucothi. Romans discovered the Dolaucothi
vein after the
invasion, in about 74 AD, and a settlement was soon set up in the Cothi Valley protected by a
fort. They used
hydraulic mining methods on a large scale to prospect for the veins of ore, especially a now redundant form of mining known as
hushing. It involved building numerous
aqueducts to supply water to the minehead where it was stored in large
reservoirs and tanks. When a full tank was opened, the wave of water sluiced away the overburden to expose the bedrock underneath and any gold veins. The rock was attacked by
fire-setting to heat the rock, which would then be quenched with a stream of water. The
thermal shock cracked the rock, enabling it to be removed, aided by further streams of water from the overhead tanks. They used similar methods to work
cassiterite deposits in
Cornwall and
lead ore in the
Pennines. The methods had been developed by the Romans in
Spain in 25 AD to exploit large
alluvial gold deposits, the largest site being at
Las Medulas, where seven long aqueducts were built to tap local rivers and to sluice the deposits.
They followed the ore veins underground once opencast mining was no longer feasible. At
Dolaucothi they stoped out the veins, and drove
adits through barren rock to drain the stopes. Alternatively, the veins may have been trenched, keeping the upper part open to the air. At deeper levels,
stoping will have been necessary. The same adits were also used to ventilate the workings, especially important when
fire-setting was used. At other parts of the site, they penetrated the
water table and dewatered the mines using several kinds of machine, especially
reverse overshot water-wheels. They were used extensively in the
copper mines at
Rio Tinto in Spain, where one sequence comprised 16 such wheels arranged in pairs, and lifting water about 80 feet. They were worked as treadmills with miners standing on the top slats. Many examples of such devices have been found in old Roman mines and some examples are now preserved in the
British Museum and the
National Museum of Wales.
Lead and
silver were widely exploited during the Roman period, in
Wales, the
Mendips and
Pennines. A lead-silver mine at
Charterhouse, Somerset for example, was guarded by a small
fort and was next to the mine workings and settlement for the miners. Lead pigs have been found at several localities in Britain, and mining was so successful, that the Spanish complained about over-production depressing the market. The silver was valuable bullion, while the lead found numerous applications, especially in roofing and plumbing.
There were many iron mines in
Roman Britain. The index to the Ordnance Survey Map of Roman Britain lists 33 iron mines: 67% of these are in the
Weald and 15% in the
Forest of Dean. The majority of mine workers were
slaves. The work conditions were poor, and up to 12% of miners died every year.
North America
In
North America there are ancient, prehistoric
copper mines along
Lake Superior. "Indians availed themselves of this copper starting at least 5000 years ago," and copper tools, arrowheads, and other
artifacts that were part of an extensive native trade network have been discovered. In addition,
obsidian,
flint, and other minerals were mined, worked, and traded. While the early French explorers that encountered the sites made no use of the metals due to the difficulties in transporting it, the copper was eventually traded throughout the continent along major river routes. In
Manitoba, Canada, there also are ancient quartz mines near Waddy Lake and surrounding regions.
In the early colonial history of the Americas, "native gold and silver was quickly expropriated and sent back to Spain in fleets of gold- and silver-laden galleons."
Turquoise dated at 700 A.D. was mined in
pre-Columbian America; in the Cerillos Mining District in
New Mexico, estimates are that "about 15,000 tons of rock had been removed from Mt Chalchihuitl using stone tools before 1700."
Mining in the
United States became prevalent in the
19th century. As with the
California Gold Rush in the mid 1800s, mining for minerals and precious metals alongside
ranching was very important in the
Westward Expansion to the Pacific coast. With the exploration of the West, mining camps were established and "expressed a distinctive spirit, an enduring legacy to the new nation;" Gold Rushers would experience the same problems as the Land Rushers of the transient West that preceded them. Aided by railroads, many traveled West for work opportunities in mining. Western cities such as
Denver and
Sacramento originated as mining towns.
Procedure
Steps of process
- Prospecting or Exploration to find and then define the extent and value of ore where it's located ("ore body")
- Conduct resource estimation to mathematically estimate the size and grade of the deposit
- Conduct a pre-feasibility study to determine the theoretical economics of the ore deposit. This identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work.
- Conduct a feasibility study to evaluate the financial viability, technical and financial risks and robustness of the project and make a decision as whether to develop or walk away from a proposed mine project. This includes mine planning to evaluate the economically recoverable portion of the deposit, the metallurgy and ore recoverability, marketability and payability of the ore concentrates, engineering, milling and infrastructure costs, finance and equity requirements and 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 and building of mine plant and equipment
- The operation of the mine in an active sense
- Reclamation to make land where a mine had been suitable for future use
Techniques
Mining techniques can be divided into two basic
excavation types:
In-situ leach is a particular mining technique that's used to mine minerals (
potash,
potassium chloride,
sodium chloride,
sodium sulfate and
uranium oxide) which dissolve in water.
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).
Environmental effects
Environmental issues can include
erosion, formation of
sinkholes, loss of
biodiversity, and contamination of
groundwaters and surface water by chemicals from the mining process and products.
Modern mining companies in some countries are required to follow environmental and rehabilitation codes, ensuring the area mined is returned to close to its original state. In some countries with pristine environments, such as large parts of
Australia, this is impossible despite the best intentions. Some mining methods have devastating environmental and public health effects.
Mining can have adverse effects on surrounding surface and ground water if protection measures are not exercised. The result can be unnaturally high concentrations of some chemical elements, notably arsenic and sulfuric acid, over a significantly large area of surface or subsurface. Coal mining releases approximately twenty toxic 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 in which massive 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
» Acid mine drainage, exemplified by the cases of the
Berkeley Lake Mine, and the
Wheal Jane Mine
» Dissolution and transport of dissolved metals and heavy metals by run-off and ground waters, an example being the
Britannia Mine, a former copper mine near Vancouver, British Columbia.
Tar Creek, an abandoned mining area in
Picher, Oklahoma that's 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.
» Long-term storage of tailings and dust, which can be easily blown off site by wind, an example being
Scouriotissa, an abandoned copper mine in
Cyprus.
» Erosion of exposed hillsides, mine dumps, tailings dams and resultant
siltation of drainages, creeks and rivers, the prime example being the giant
Ok Tedi Mine in
Papua New Guinea.
» In areas of wilderness mining may cause habitat destruction and destruction or disturbance of
ecosystems, and in areas of farming it may disturb or destroy productive grazing and cropping lands. In urbanised environments mining may produce
noise pollution, dust pollution and visual pollution.
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. Modern mining practises aim to lessen environmental impacts from mining, and the ultimate aim is to return the local environment to as close to pristine as is possible. In many cases, the most significant environmental impact longer-term is visual, with pits and mine dumps prominent landscape features.
To ensure completion of
reclamation (restoring mine land) most governments and regulatory authorities around the world require 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 in the United States alone. 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, please see
Restoration ecology.
Mining industry
Overview
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 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 dependent on public investment. The mining sector is typically large and multi-national companies sustained by mineral production from their mining operations.
Employment
United States
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's 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
United States
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 are often very high profile, such as the Quecreek Mine Rescue saving 9 trapped Pennsylvania coal miners in 2002.
Mining ventilation is often seen to be a safety concern for many miners and their families. Poor ventilation of the mines causes exposure to harmful gases, heat and dust inside sub-surface mines. These can cause harmful physiological effects, even death. The concentration of methane and other airborne contaminants underground can generally be controlled by dilution (ventilation), capture before entering the host air stream (methane drainage), or isolation (seals and stoppings).
Methane gas is a common source of ignition for explosions in coal mines and can propagate into the more violent coal dust explosions. Explosions can be prevented or mitigated by eliminating ignition sources, minimizing methane concentrations and coal dust accumulations, generalized rock dusting, and by using passive and active barriers to suppress propagating explosions.
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
Heavy machinery is needed in mining for exploration and development, to remove and stockpile overburden, to break and remove rocks of diverse hardness and toughness, and to process the ore as well as for reclamation. 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.
Trams are used to transport miners, minerals and waste.
Mining machinery manufacturers include Atlas Copco, Joy Mining Machinery, Bucyrus International, Caterpillar, Komatsu, Volvo, Hitachi, Terex, Dresser Industries, Kawasaki, Eimco Elecon India Limited, and Liebherr.
Placer mining is a type of surface mining, usually for gold, tin, and other metals, and gemstones. Ore, typically unconsolidated gravels (alluvium), is fed into machinery that may consist of a hopper, shaking screen or trommel which frees the minerals from the gravels. The target minerals are then concentrated using sluices or jigs.
Abandoned mines
The number of abandoned mines in the United States remains an unknown, ranging "from the National Park Service's tally of 2,500 on its lands, to the Mineral Policy Center's assessment of 560,000 abandoned mines on public and privately owned lands." 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.
In the U.S., the estimation is 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. Since weather may have eroded the earth/rock surrounding it, the entrance to an old mine in particular can be very dangerous. Old mine workings, caves, etc. are commonly hazardous simply due to the lack of oxygen in the air (a condition in mines known as blackdamp). Blackdamp is a deadly killer which provides no warning to any individual or group of individuals entering such an environment.
Every year, dozens are injured or killed in recreational accidents on mine property. It is only fair to note, however, that the majority of the deaths are unrelated to mine exploration. Drownings in open quarries and ATV accidents on abandoned mine properties are the main cause of accidental death. The U.S. Department of Labor notes that since 1999, "more than 200 people have died in recreational accidents at surface and underground active and abandoned operations across the country." Due to these circumstances, MSHA (Mine Safety and Health Administration) launched the "Stay Out – Stay Alive" campaign, which 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.
In the U.S., the Abandoned Mine Land Initiative, launched by the Western Governor's Association and the National Mining Association is also an effort focusing on reporting the number of high-priority AML sites. The initiative identifies, measures and reports on the progress of current reclamation cleanup programs on an annual basis. In the Americas region, the United Nations Environment Programme (UNEP) and the Chilean Copper Commission (COHILCO) co-hosted a workshop to address the problem of abandoned or "orphaned" mines. Including a representative from the UN, ten countries were represented from North, Central and South America with an eleventh participant being Japan.
Records
The deepest mine in the world: Savuka Mine in the North West Province, South Africa at 3,774 meters
The deepest open pit mine in the world: Bingham Canyon Mine in Bingham Canyon, Utah, USA at over 1,200 meters
The largest and second deepest open pit copper mine in the world: Chuquicamata in Chuquicamata, Chile at 900 meters, 940.600 Tons of fine copper and 17.700 Tons of molybdenum
The largest underground mine: El Teniente, in Rancagua, Chile, 2400 kilometers of underground drifts, 418.000 Tons of copper yearly
The deepest mine in Europe: Pyhäsalmi Mine in Pyhäjärvi, Finland at 1,444 meters
The second deepest mine in Europe: Boulby Mine England at 1,400 meters (shaft depth 1,100 meters)
Sweden's largest underground mine: Kirunavaara mine in Kiruna, Sweden, 450 kilometers of roads, 40 million tonnes of ore produced yearly, depth 1270 meters.
The deepest borehole in the world: Kola Superdeep Borehole at 12,262 meters. This, however, isn't a matter of mining but rather related to scientific drilling.Further Information
Get more info on 'Mining'.
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