Surface coal mining
Sulfur miner with 90 kg of sulfur carried from the floor of the Ijen Volcano (2015)
Simplified world active mining map
Mining is the extraction of valuable minerals or other geological materials from the earth, usually from an orebody, lode, vein, seam, reef or placer deposit. These deposits form a mineralized package that is of economic interest to the miner.
Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. Mining is required to obtain any material that cannot be grown through agricultural processes, or feasibly created artificially in a laboratory or factory. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.
Mining of stones and metal has been a human activity since pre-historic times. Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials, and final reclamation of the land after the mine is closed. De Re Metallica, Georgius Agricola, 1550, Book I, Para. 1.
Mining operations usually create a negative environmental impact,
both during the mining activity and after the mine has closed. Hence,
most of the world's nations have passed regulations to decrease the
impact. Work safety has long been a concern as well, and modern practices have significantly improved safety in mines.
Levels of metals recycling
are generally low. Unless future end-of-life recycling rates are
stepped up, some rare metals may become unavailable for use in a variety
of consumer products. Due to the low recycling rates, some landfills now contain higher concentrations of metal than mines themselves.
History
Prehistoric mining
Chalcolithic copper mine in Timna Valley, Negev Desert
Since the beginning of civilization, people have used stone, ceramics and, later, metals found close to the Earth's surface. These were used to make early tools and weapons; for example, high quality flint found in northern France, southern England and Poland was used to create flint tools. 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 and Krzemionki are especially famous, and like most other flint mines, are Neolithic in origin (c. 4000–3000 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 Ngwenya Mine in Swaziland, which radiocarbon dating shows to be about 43,000 years old. At this site Paleolithic humans mined hematite to make the red pigment ocher. Mines of a similar age in Hungary are believed to be sites where Neanderthals may have mined flint for weapons and tools.
Ancient Egypt
Ancient Egyptians mined malachite at Maadi. At first, Egyptians
used the bright green malachite stones for ornamentation and pottery.
Later, between 2613 and 2494 BC, large building projects required
expeditions abroad to the area of Wadi Maghareh in order to secure minerals and other resources not available in Egypt itself. Quarries for turquoise and copper were also found at Wadi Hammamat, Tura, Aswan and various other Nubian sites on the Sinai Peninsula and at Timna.
Mining in Egypt occurred in the earliest dynasties. The gold mines of Nubia were among the largest and most extensive of any in Ancient Egypt. These mines are described by the Greek author Diodorus Siculus, who mentions fire-setting
as one method used to break down the hard rock holding the gold. One of
the complexes is shown in one of the earliest known maps. The miners
crushed the ore and ground it to a fine powder before washing the powder
for the gold dust.
Ancient Greek and Roman mining
Ancient Roman development of the Dolaucothi Gold Mines, Wales
Mining in Europe has a very long history. Examples include the silver mines of Laurium, which helped support the Greek city state of Athens.
Although they had over 20,000 slaves working them, their technology was
essentially identical to their Bronze Age predecessors. At other mines, such as on the island of Thassos, marble was quarried by the Parians after they arrived in the 7th century BC.
The marble was shipped away and was later found by archaeologists to
have been used in buildings including the tomb of Amphipolis. Philip II of Macedon, the father of Alexander the Great, captured the gold mines of Mount Pangeo in 357 BC to fund his military campaigns. He also captured gold mines in Thrace for minting coinage, eventually producing 26 tons per year.
However, it was the Romans who developed large scale mining methods, especially the use of large volumes of water brought to the mine head by numerous aqueducts. The water was used for a variety of purposes, including removing overburden and rock debris, called hydraulic mining, as well as washing comminuted, or crushed, ores and driving simple machinery.
The Romans used hydraulic mining methods on a large scale to prospect for the veins of ore, especially a now-obsolete form of mining known as hushing. They built numerous aqueducts to supply water to the minehead. There, the water stored in large reservoirs and tanks. When a full tank was opened, the flood of water sluiced away the overburden to expose the bedrock underneath and any gold veins. The rock was then worked upon by fire-setting to heat the rock, which would be quenched with a stream of water. The resulting thermal shock
cracked the rock, enabling it to be removed by further streams of water
from the overhead tanks. The Roman miners 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 tapped local rivers and sluiced the deposits. Spain was one of the most important mining regions, but all regions of the Roman Empire were exploited. In Great Britain the natives had mined minerals for millennia, but after the Roman conquest, the scale of the operations increased dramatically, as the Romans needed Britannia's resources, especially gold, silver, tin, and lead.
Roman techniques were not limited to surface mining. They
followed the ore veins underground once opencast mining was no longer
feasible. At Dolaucothi they stoped out the veins and drove adits through bare rock to drain the stopes. 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 machines, especially reverse overshot water-wheels. These 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 24 meters (79 ft). 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.
Medieval Europe
Agricola, author of De Re Metallica
Gallery, 12th to 13th century, Germany
Mining as an industry underwent dramatic changes in medieval Europe. The mining industry in the early Middle Ages was mainly focused on the extraction of copper and iron. Other precious metals were also used, mainly for gilding or coinage. Initially, many metals were obtained through open-pit mining,
and ore was primarily extracted from shallow depths, rather than
through deep mine shafts. Around the 14th century, the growing use of
weapons, armor, stirrups,
and horseshoes greatly increased the demand for iron. Medieval knights,
for example, were often laden with up to 100 pounds (45 kg) of plate or
chain link armor in addition to swords, lances and other weapons. The overwhelming dependency on iron for military purposes spurred iron production and extraction processes.
The silver crisis of 1465 occurred when all mines had reached
depths at which the shafts could no longer be pumped dry with the
available technology. Although an increased use of banknotes, credit and copper coins during this period did decrease the value of, and dependence on, precious metals, gold and silver still remained vital to the story of medieval mining.
Due to differences in the social structure of society, the
increasing extraction of mineral deposits spread from central Europe to
England in the mid-sixteenth century. On the continent, mineral deposits
belonged to the crown, and this regalian right was stoutly maintained.
But in England, royal mining rights were restricted to gold and silver
(of which England had virtually no deposits) by a judicial decision of
1568 and a law in 1688. England had iron, zinc, copper, lead, and tin
ores. Landlords who owned the base metals and coal under their estates
then had a strong inducement to extract these metals or to lease the
deposits and collect royalties from mine operators. English, German, and
Dutch capital combined to finance extraction and refining. Hundreds of
German technicians and skilled workers were brought over; in 1642 a
colony of 4,000 foreigners was mining and smelting copper at Keswick in the northwestern mountains.
Use of water power in the form of water mills
was extensive. The water mills were employed in crushing ore, raising
ore from shafts, and ventilating galleries by powering giant bellows. Black powder was first used in mining in Selmecbánya, Kingdom of Hungary (now Banská Štiavnica, Slovakia) in 1627. Black powder allowed blasting of rock and earth to loosen and reveal ore veins. Blasting was much faster than fire-setting and allowed the mining of previously impenetrable metals and ores. In 1762, the world's first mining academy was established in the same town there.
The widespread adoption of agricultural innovations such as the iron plowshare,
as well as the growing use of metal as a building material, was also a
driving force in the tremendous growth of the iron industry during this
period. Inventions like the arrastra
were often used by the Spanish to pulverize ore after being mined. This
device was powered by animals and used the same principles used for
grain threshing.
Much of the knowledge of medieval mining techniques comes from books such as Biringuccio’s De la pirotechnia and probably most importantly from Georg Agricola's De re metallica
(1556). These books detail many different mining methods used in German
and Saxon mines. A prime issue in medieval mines, which Agricola
explains in detail, was the removal of water from mining shafts. As
miners dug deeper to access new veins, flooding became a very real
obstacle. The mining industry became dramatically more efficient and
prosperous with the invention of mechanical and animal driven pumps.
Classical Philippine civilization
The image of a Maharlika class of the Philippine Society, depicted in Boxer Codex that the Gold used as a form of Jewelry (ca.1400).
Mining in the Philippines began around 1000 BC. The early Filipinos
worked various mines of gold, silver, copper and iron. Jewels, gold
ingots, chains, calombigas and earrings were handed down from antiquity
and inherited from their ancestors. Gold dagger handles, gold dishes,
tooth plating, and huge gold ornamets were also used.
In Laszlo Legeza's "Tantric elements in pre-Hispanic Philippines Gold
Art", he mentioned that gold jewelry of Philippine origin was found in Ancient Egypt. According to Antonio Pigafetta, the people of Mindoro
possessed great skill in mixing gold with other metals and gave it a
natural and perfect appearance that could deceive even the best of
silversmiths.
The natives were also known for the jewelries made of other precious
stones such as carnelian, agate and pearl. Some outstanding examples of
Philippine jewelry included necklaces, belts, armlets and rings placed
around the waist.
The Americas
Lead mining in the upper Mississippi River region of the U.S., 1865.
During prehistoric times, large amounts of copper was mined along Lake Superior's Keweenaw Peninsula and in nearby Isle Royale; metallic copper was still present near the surface in colonial times. Indigenous peoples used Lake Superior copper from at least 5,000 years ago; 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. Early French explorers who encountered the sites made no use of the metals due to the difficulties of transporting them, but the copper was eventually traded throughout the continent along major river routes.
Miners at the Tamarack Mine in Copper Country, Michigan, U.S. in 1905.
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," the gold and silver originating mostly from mines in Central and South America. Turquoise dated at 700 AD 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."
In 1727, Louis Denys (Denis) (1675–1741), sieur de La Ronde – brother of Simon-Pierre Denys de Bonaventure and the son-in-law of René Chartier – took command of Fort La Pointe at Chequamegon Bay;
where natives informed him of an island of copper. La Ronde obtained
permission from the French crown to operate mines in 1733, becoming "the
first practical miner on Lake Superior"; seven years later, mining was
halted by an outbreak between Sioux and Chippewa tribes.
Mining in the United States became prevalent in the 19th century, and the General Mining Act of 1872 was passed to encourage mining of federal lands. As with the California Gold Rush in the mid-19th century, mining for minerals and precious metals, along with ranching, was a driving factor 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.
When new areas were explored, it was usually the gold (placer and
then lode) and then silver that were taken into possession and
extracted first. Other metals would often wait for railroads or canals,
as coarse gold dust and nuggets do not require smelting and are easy to
identify and transport.
Modern period
View showing miners' clothes suspended by pulleys, also wash basins and ventilation system, Kirkland Lake, Ontario, 1936.
In the early 20th century, the gold and silver rush to the western United States also stimulated mining for coal as well as base metals
such as copper, lead, and iron. Areas in modern Montana, Utah, Arizona,
and later Alaska became predominate suppliers of copper to the world,
which was increasingly demanding copper for electrical and households
goods.
Canada's mining industry grew more slowly than did the United States'
due to limitations in transportation, capital, and U.S. competition;
Ontario was the major producer of the early 20th century with nickel,
copper, and gold.
Meanwhile, Australia experienced the Australian gold rushes and by the 1850s was producing 40% of the world's gold, followed by the establishment of large mines such as the Mount Morgan Mine, which ran for nearly a hundred years, Broken Hill ore deposit (one of the largest zinc-lead ore deposits), and the iron ore mines at Iron Knob.
After declines in production, another boom in mining occurred in the
1960s. Now, in the early 21st century, Australia remains a major world
mineral producer.
As the 21st century begins, a globalized mining industry of large multinational corporations has arisen. Peak minerals and environmental impacts have also become a concern. Different elements, particularly rare earth minerals, have begun to increase in demand as a result of new technologies.
Mine development and lifecycle
Schematic of a cut and fill mining operation in hard rock.
The process of mining from discovery of an ore body through
extraction of minerals and finally to returning the land to its natural
state consists of several distinct steps. The first is discovery of the
ore body, which is carried out through prospecting or exploration to find and then define the extent, location and value of the ore body. This leads to a mathematical resource estimation to estimate the size and grade of the deposit.
This estimation is used to conduct a 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. The next step is to conduct a feasibility study to evaluate the financial viability, the technical and financial risks, and the robustness of the project.
This is when the mining company makes the decision whether to
develop the mine or to walk away from the 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 concerns, milling and infrastructure costs,
finance and equity requirements, and an analysis of the proposed mine
from the initial excavation all the way through to reclamation. The
proportion of a deposit that is economically recoverable is dependent on
the enrichment factor of the ore in the area.
To gain access to the mineral deposit within an area it is often necessary to mine through or remove waste material
which is not of immediate interest to the miner. The total movement of
ore and waste constitutes the mining process. Often more waste than ore
is mined during the life of a mine, depending on the nature and location
of the ore body. Waste removal and placement is a major cost to the
mining operator, so a detailed characterization of the waste material
forms an essential part of the geological exploration program for a
mining operation.
Once the analysis determines a given ore body is worth
recovering, development begins to create access to the ore body. The
mine buildings and processing plants are built, and any necessary
equipment is obtained. The operation of the mine to recover the ore
begins and continues as long as the company operating the mine finds it
economical to do so. Once all the ore that the mine can produce
profitably is recovered, reclamation begins to make the land used by the mine suitable for future use.
Mining techniques
Underground longwall mining.
Mining techniques can be divided into two common excavation types: surface mining and sub-surface (underground) mining.
Today, surface mining is much more common, and produces, for example,
85% of minerals (excluding petroleum and natural gas) in the United
States, including 98% of metallic ores.
Targets are divided into two general categories of materials: placer deposits, consisting of valuable minerals contained within river gravels, beach sands, and other unconsolidated materials; and lode deposits,
where valuable minerals are found in veins, in layers, or in mineral
grains generally distributed throughout a mass of actual rock. Both
types of ore deposit, placer or lode, are mined by both surface and
underground methods.
Some mining, including much of the rare earth elements and uranium mining, is done by less-common methods, such as in-situ leaching:
this technique involves digging neither at the surface nor underground.
The extraction of target minerals by this technique requires that they
be soluble, e.g., potash, potassium chloride, sodium chloride, sodium sulfate, which dissolve in water. Some minerals, such as copper minerals and uranium oxide, require acid or carbonate solutions to dissolve.
Surface mining
Surface mining
is done by removing (stripping) surface vegetation, dirt, and, if
necessary, layers of bedrock in order to reach buried ore deposits.
Techniques of surface mining include: open-pit mining, which is the recovery of materials from an open pit in the ground, quarrying, identical to open-pit mining except that it refers to sand, stone and clay; strip mining, which consists of stripping surface layers off to reveal ore/seams underneath; and mountaintop removal,
commonly associated with coal mining, which involves taking the top of a
mountain off to reach ore deposits at depth. Most (but not all) placer
deposits, because of their shallowly buried nature, are mined by surface
methods. Finally, landfill mining involves sites where landfills are excavated and processed. Landfill mining has been thought of as a solution to dealing with long-term methane emissions and local pollution
Underground mining
Mantrip used for transporting miners within an underground mine
Sub-surface mining consists of digging tunnels or shafts into the
earth to reach buried ore deposits. Ore, for processing, and waste rock,
for disposal, are brought to the surface through the tunnels and
shafts. Sub-surface mining can be classified by the type of access
shafts used, the extraction method or the technique used to reach the
mineral deposit. Drift mining utilizes horizontal access tunnels, slope mining uses diagonally sloping access shafts, and shaft mining utilizes vertical access shafts. Mining in hard and soft rock formations require different techniques.
Other methods include shrinkage stope mining, which is mining upward, creating a sloping underground room, long wall mining, which is grinding a long ore surface underground, and room and pillar
mining, which is removing ore from rooms while leaving pillars in place
to support the roof of the room. Room and pillar mining often leads to retreat mining,
in which supporting pillars are removed as miners retreat, allowing the
room to cave in, thereby loosening more ore. Additional sub-surface
mining methods include hard rock mining,
which is mining of hard rock (igneous, metamorphic or sedimentary)
materials, bore hole mining, drift and fill mining, long hole slope
mining, sub level caving, and block caving.
Highwall mining
Caterpillar Highwall Miner HW300 – Technology Bridging Underground and Open Pit Mining
Highwall mining is another form of surface mining that evolved from
auger mining. In Highwall mining, the coal seam is penetrated by a
continuous miner propelled by a hydraulic Pushbeam Transfer Mechanism
(PTM). A typical cycle includes sumping (launch-pushing forward) and
shearing (raising and lowering the cutterhead boom to cut the entire
height of the coal seam). As the coal recovery cycle continues, the
cutterhead is progressively launched into the coal seam for 19.72 feet
(6.01 m). Then, the Pushbeam Transfer Mechanism (PTM) automatically
inserts a 19.72-foot (6.01 m) long rectangular Pushbeam (Screw-Conveyor
Segment) into the center section of the machine between the Powerhead
and the cutterhead. The Pushbeam system can penetrate nearly 1,000 feet
(300 m) into the coal seam. One patented Highwall mining system uses
augers enclosed inside the Pushbeam that prevent the mined coal from
being contaminated by rock debris during the conveyance process. Using a
video imaging and/or a gamma ray sensor and/or other Geo-Radar systems
like a coal-rock interface detection sensor (CID), the operator can see
ahead projection of the seam-rock interface and guide the continuous
miner's progress. Highwall mining can produce thousands of tons of coal
in contour-strip operations with narrow benches, previously mined areas,
trench mine applications and steep-dip seams with controlled
water-inflow pump system and/or a gas (inert) venting system.
Machines
The Bagger 288 is a bucket-wheel excavator used in strip mining. It is also the largest land vehicle of all time.
A Bucyrus Erie 2570 dragline and CAT 797 haul truck at the North Antelope Rochelle opencut coal mine
Heavy machinery
is used in mining to explore and develop sites, to remove and stockpile
overburden, to break and remove rocks of various hardness and
toughness, to process the ore, and to carry out reclamation projects
after the mine is closed. Bulldozers, drills, explosives and trucks are
all necessary for excavating the land. In the case of placer mining, unconsolidated gravel, or alluvium, is fed into machinery consisting of a hopper and a shaking screen or trommel which frees the desired minerals from the waste gravel. The minerals are then concentrated using sluices or jigs.
Large drills are used to sink shafts, excavate stopes, and obtain samples for analysis. Trams
are used to transport miners, minerals and waste. Lifts carry miners
into and out of mines, and move rock and ore out, and machinery in and
out, of underground mines. Huge trucks, shovels and cranes are employed
in surface mining to move large quantities of overburden and ore.
Processing plants utilize large crushers, mills, reactors, roasters and
other equipment to consolidate the mineral-rich material and extract the
desired compounds and metals from the ore.
Processing
Once the mineral is extracted, it is often then processed. The science of extractive metallurgy
is a specialized area in the science of metallurgy that studies the
extraction of valuable metals 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). Processing of placer ore material consists of gravity-dependent methods of separation, such as sluice
boxes. Only minor shaking or washing may be necessary to disaggregate
(unclump) the sands or gravels before processing. Processing of ore from
a lode mine, whether it is a surface or subsurface mine, requires that
the rock ore be crushed and pulverized before extraction of the valuable
minerals begins. After lode ore is crushed, recovery of the valuable
minerals is done by one, or a combination of several, mechanical and
chemical techniques.
Since most metals are present in ores as oxides or sulfides, the metal needs to be reduced to its metallic form. This can be accomplished through chemical means such as smelting or through electrolytic reduction, as in the case of aluminum. Geometallurgy combines the geologic sciences with extractive metallurgy and mining.
In 2018, led by Chemistry and Biochemistry professor Bradley D. Smith, University of Notre Dame
researchers "invented a new class of molecules whose shape and size
enable them to capture and contain precious metal ions," reported in a
study published by the Journal of the American Chemical Society. The new method "converts gold-containing ore into chloroauric acid
and extracts it using an industrial solvent. The container molecules
are able to selectively separate the gold from the solvent without the
use of water stripping." The newly developed molecules can eliminate
water stripping, whereas mining traditionally "relies on a 125-year-old
method that treats gold-containing ore with large quantities of
poisonous sodium cyanide...
this new process has a milder environmental impact and that, besides
gold, it can be used for capturing other metals such as platinum and
palladium," and could also be used in urban mining processes that remove
precious metals from wastewater streams.
Environmental effects
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 soil, groundwater and surface water
by chemicals from mining processes. In some cases, additional forest
logging is done in the vicinity of mines to create space for the storage
of the created debris and soil.
Contamination resulting from leakage of chemicals can also affect the
health of the local population if not properly controlled. Extreme examples of pollution from mining activities include coal fires, which can last for years or even decades, producing massive amounts of environmental damage.
Mining companies in most countries are required to follow
stringent environmental and rehabilitation codes in order to minimize
environmental impact and avoid impacting human health. These codes and
regulations all require the common steps of environmental impact assessment, development of environmental management plans, mine closure planning (which must be done before the start of mining operations), and environmental monitoring
during operation and after closure. However, in some areas,
particularly in the developing world, government regulations may not be
well enforced.
For major mining companies and any company seeking international
financing, there are a number of other mechanisms to enforce good
environmental standards. These generally relate to financing standards
such as the Equator Principles, IFC environmental standards, and criteria for Socially responsible investing. Mining companies have used this oversight from the financial sector to argue for some level of industry self-regulation. In 1992, a Draft Code of Conduct for Transnational Corporations was proposed at the Rio Earth Summit
by the UN Centre for Transnational Corporations (UNCTC), but the
Business Council for Sustainable Development (BCSD) together with the
International Chamber of Commerce (ICC) argued successfully for
self-regulation instead.
This was followed by the Global Mining Initiative which was begun
by nine of the largest metals and mining companies and which led to the
formation of the International Council on Mining and Metals,
whose purpose was to "act as a catalyst" in an effort to improve social
and environmental performance in the mining and metals industry
internationally.
The mining industry has provided funding to various conservation
groups, some of which have been working with conservation agendas that
are at odds with an emerging acceptance of the rights of indigenous
people – particularly the right to make land-use decisions.
Certification of mines with good practices occurs through the International Organization for Standardization (ISO). For example, ISO 9000 and ISO 14001,
which certify an "auditable environmental management system", involve
short inspections, although they have been accused of lacking rigor. Certification is also available through Ceres' Global Reporting Initiative,
but these reports are voluntary and unverified. Miscellaneous other
certification programs exist for various projects, typically through
nonprofit groups.
The purpose of a 2012 EPS PEAKS paper was to provide evidence on policies managing ecological costs and maximize socio-economic
benefits of mining using host country regulatory initiatives. It found
existing literature suggesting donors encourage developing countries to:
- Make the environment-poverty link and introduce cutting-edge wealth measures and natural capital accounts.
- Reform old taxes in line with more recent financial innovation, engage directly with the companies, enacting land use and impact assessments, and incorporate specialised support and standards agencies.
- Set in play transparency and community participation initiatives using the wealth accrued.
Waste
Ore mills generate large amounts of waste, called tailings. For example, 99 tons of waste are generated per ton of copper, with even higher ratios in gold mining – because only 5.3 g of gold is extracted per ton of ore, a ton of gold produces 200,000 tons of tailings.
(As time goes on and richer deposits are exhausted – and technology
improves to permit – this number is going down to .5 g and less.) These
tailings can be toxic. Tailings, which are usually produced as a slurry, are most commonly dumped into ponds made from naturally existing valleys. These ponds are secured by impoundments (dams or embankment dams).
In 2000 it was estimated that 3,500 tailings impoundments existed, and
that every year, 2 to 5 major failures and 35 minor failures occurred; for example, in the Marcopper mining disaster at least 2 million tons of tailings were released into a local river.
In central Finland, Talvivaara Terrafame polymetal mine waste effluent
since 2008 and numerous leaks of saline mine water has resulted in
ecological collapse of nearby lake. Subaqueous tailings disposal is another option.
The mining industry has argued that submarine tailings disposal (STD),
which disposes of tailings in the sea, is ideal because it avoids the
risks of tailings ponds; although the practice is illegal in the United
States and Canada, it is used in the developing world.
The waste is classified as either sterile or mineralized, with
acid generating potential, and the movement and storage of this material
forms a major part of the mine planning process. When the mineralized
package is determined by an economic cut-off, the near-grade mineralized
waste is usually dumped separately with view to later treatment should
market conditions change and it becomes economically viable. Civil
engineering design parameters are used in the design of the waste dumps,
and special conditions apply to high-rainfall areas and to seismically
active areas. Waste dump designs must meet all regulatory requirements
of the country in whose jurisdiction the mine is located. It is also
common practice to rehabilitate dumps to an internationally acceptable
standard, which in some cases means that higher standards than the local
regulatory standard are applied.
Renewable energy and mining
Many mining sites are remote and not connected to the grid. Electricity is typically generated with diesel generators.
Due to high transportation cost and theft during transportation the
cost for generating electricity is normally high. Renewable energy
applications are becoming an alternative or amendment. Both solar and wind power plants can contribute in saving diesel costs at mining sites. Renewable energy applications have been built at mining sites.
Cost savings can reach up to 70%.
Mining industry
Mining exists in many countries. London is known as the capital of global "mining houses" such as Rio Tinto Group, BHP Billiton, and Anglo American PLC.
The US mining industry is also large, but it is dominated by the coal
and other nonmetal minerals (e.g., rock and sand), and various
regulations have worked to reduce the significance of mining in the
United States. In 2007 the total market capitalization
of mining companies was reported at US$962 billion, which compares to a
total global market cap of publicly traded companies of about
US$50 trillion in 2007. In 2002, Chile and Peru were reportedly the major mining countries of South America. The mineral industry of Africa
includes the mining of various minerals; it produces relatively little
of the industrial metals copper, lead, and zinc, but according to one
estimate has as a percent of world reserves 40% of gold, 60% of cobalt,
and 90% of the world's platinum group metals. Mining in India is a significant part of that country's economy. In the developed world, mining in Australia, with BHP Billiton founded and headquartered in the country, and mining in Canada are particularly significant. For rare earth minerals mining, China reportedly controlled 95% of production in 2013.
The Bingham Canyon Mine of Rio Tinto's subsidiary, Kennecott Utah Copper.
While exploration and mining can be conducted by individual
entrepreneurs or small businesses, 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, companies, most of them publicly listed. It can be
argued that what is referred to as the 'mining industry' is actually two
sectors, one specializing in exploration for new resources and the
other in mining those resources. The exploration sector is typically
made up of individuals and small mineral resource companies, called
"juniors", which are dependent on venture capital. The mining sector is
made up of large multinational companies that are sustained by
production from their mining operations. Various other industries such
as equipment manufacture, environmental testing, and metallurgy analysis
rely on, and support, the mining industry throughout the world.
Canadian stock exchanges have a particular focus on mining companies,
particularly junior exploration companies through Toronto's TSX Venture Exchange; Canadian companies raise capital on these exchanges and then invest the money in exploration globally.
Some have argued that below juniors there exists a substantial sector
of illegitimate companies primarily focused on manipulating stock
prices.
Mining operations can be grouped into five major categories in
terms of their respective resources. These are oil and gas extraction,
coal mining, metal ore mining, nonmetallic mineral mining and quarrying,
and mining support activities.
Of all of these categories, oil and gas extraction remains one of the
largest in terms of its global economic importance. Prospecting
potential mining sites, a vital area of concern for the mining industry,
is now done using sophisticated new technologies such as seismic
prospecting and remote-sensing satellites. Mining is heavily affected by
the prices of the commodity minerals, which are often volatile. The 2000s commodities boom
("commodities supercycle") increased the prices of commodities, driving
aggressive mining. In addition, the price of gold increased
dramatically in the 2000s, which increased gold mining;
for example, one study found that conversion of forest in the Amazon
increased six-fold from the period 2003–2006 (292 ha/yr) to the period
2006–2009 (1,915 ha/yr), largely due to artisanal mining.
Corporate classifications
Mining companies can be classified based on their size and financial capabilities:
- Major companies are considered to have an adjusted annual mining-related revenue of more than US$500 million, with the financial capability to develop a major mine on its own.
- Intermediate companies have at least $50 million in annual revenue but less than $500 million.
- Junior companies rely on equity financing as their principal means of funding exploration. Juniors are mainly pure exploration companies, but may also produce minimally, and do not have a revenue exceeding US$50 million.
Regulation and governance
New
regulations and a process of legislative reforms aim to improve the
harmonization and stability of the mining sector in mineral-rich
countries.
New legislation for mining industry in African countries still appears
to be an issue, but has the potential to be solved, when a consensus is
reached on the best approach.
By the beginning of the 21st century the booming and increasingly
complex mining sector in mineral-rich countries was providing only
slight benefits to local communities, especially in given the
sustainability issues. Increasing debate and influence by NGOs and local communities called for a new approaches which would also include disadvantaged communities, and work towards sustainable development even after mine closure
(including transparency and revenue management). By the early 2000s,
community development issues and resettlements became mainstream
concerns in World Bank mining projects.
Mining-industry expansion after mineral prices increased in 2003 and
also potential fiscal revenues in those countries created an omission in
the other economic sectors in terms of finances and development.
Furthermore, this highlighted regional and local demand for mining
revenues and an inability of sub-national governments to effectively use
the revenues. The Fraser Institute (a Canadian think tank) has highlighted
the environmental protection laws in developing countries, as well as
voluntary efforts by mining companies to improve their environmental
impact.
In 2007 the Extractive Industries Transparency Initiative (EITI) was mainstreamed in all countries cooperating with the World Bank in mining industry reform. The EITI operates and was implemented with the support of the EITI multi-donor trust fund, managed by the World Bank. The EITI aims to increase transparency in transactions between governments and companies in extractive industries
by monitoring the revenues and benefits between industries and
recipient governments. The entrance process is voluntary for each
country and is monitored by multiple stakeholders including governments,
private companies and civil society representatives, responsible for
disclosure and dissemination of the reconciliation report;
however, the competitive disadvantage of company-by company public
report is for some of the businesses in Ghana at least, the main
constraint.
Therefore, the outcome assessment in terms of failure or success of the
new EITI regulation does not only "rest on the government's shoulders"
but also on civil society and companies.
On the other hand, implementation has issues; inclusion or exclusion of artisanal mining
and small-scale mining (ASM) from the EITI and how to deal with
"non-cash" payments made by companies to subnational governments.
Furthermore, the disproportionate revenues the mining industry can bring
to the comparatively small number of people that it employs,
causes other problems, like a lack of investment in other less
lucrative sectors, leading to swings in government revenuebecause of
volatility in the oil markets. Artisanal mining is clearly an issue in
EITI Countries such as the Central African Republic, D.R. Congo, Guinea,
Liberia and Sierra Leone – i.e. almost half of the mining countries
implementing the EITI.
Among other things, limited scope of the EITI involving disparity in
terms of knowledge of the industry and negotiation skills, thus far
flexibility of the policy (e.g. liberty of the countries to expand
beyond the minimum requirements and adapt it to their needs), creates
another risk of unsuccessful implementation. Public awareness increase,
where government should act as a bridge between public and initiative
for a successful outcome of the policy is an important element to be
considered.
World Bank
The World Bank has been involved in mining since 1955, mainly through grants from its International Bank for Reconstruction and Development, with the Bank's Multilateral Investment Guarantee Agency offering political risk insurance.
Between 1955 and 1990 it provided about $2 billion to fifty mining
projects, broadly categorized as reform and rehabilitation, greenfield
mine construction, mineral processing, technical assistance, and
engineering. These projects have been criticized, particularly the Ferro Carajas project of Brazil, begun in 1981.
The World Bank established mining codes intended to increase foreign
investment; in 1988 it solicited feedback from 45 mining companies on
how to increase their involvement.
In 1992 the World Bank began to push for privatization of government-owned mining companies with a new set of codes, beginning with its report The Strategy for African Mining. In 1997, Latin America's largest miner Companhia Vale do Rio Doce
(CVRD) was privatized. These and other developments such as the
Philippines 1995 Mining Act led the bank to publish a third report (Assistance for Minerals Sector Development and Reform in Member Countries)
which endorsed mandatory environment impact assessments and attention
to the concerns of the local population. The codes based on this report
are influential in the legislation of developing nations. The new codes
are intended to encourage development through tax holidays, zero custom
duties, reduced income taxes, and related measures.
The results of these codes were analyzed by a group from the University
of Quebec, which concluded that the codes promote foreign investment
but "fall very short of permitting sustainable development". The observed negative correlation between natural resources and economic development is known as the resource curse.
Safety
Mining transport in Devnya, Bulgaria.
Safety has long been a concern in the mining business, especially in sub-surface mining. The Courrières mine disaster, Europe's worst mining accident, involved the death of 1,099 miners in Northern France on March 10, 1906. This disaster was surpassed only by the Benxihu Colliery accident in China on April 26, 1942, which killed 1,549 miners. While mining today is substantially safer than it was in previous decades, mining accidents
still occur. Government figures indicate that 5,000 Chinese miners die
in accidents each year, while other reports have suggested a figure as
high as 20,000. Mining accidents continue worldwide, including accidents causing dozens of fatalities at a time such as the 2007 Ulyanovskaya Mine disaster in Russia, the 2009 Heilongjiang mine explosion in China, and the 2010 Upper Big Branch Mine disaster in the United States. Mining has been identified by the National Institute for Occupational Safety and Health (NIOSH) as a priority industry sector in the National Occupational Research Agenda (NORA) to identify and provide intervention strategies regarding occupational health and safety issues. The Mining Safety and Health Administration
(MSHA) was established in 1978 to "work to prevent death, illness, and
injury from mining and promote safe and healthful workplaces for US
miners." Since its implementation in 1978, the number of miner fatalities has decreased from 242 miners in 1978 to 28 miners in 2015.
There are numerous occupational hazards associated with mining, including exposure to rockdust which can lead to diseases such as silicosis, asbestosis, and pneumoconiosis. Gases in the mine can lead to asphyxiation and could also be ignited. Mining equipment can generate considerable noise, putting workers at risk for hearing loss. Cave-ins, rock falls,
and exposure to excess heat are also known hazards. The current NIOSH
Recommended Exposure Limit (REL) of noise is 85 dBA with a 3 dBA
exchange rate and the MSHA Permissible Exposure Limit (PEL) is 90 dBA
with a 5 dBA exchange rate as an 8-hour time-weighted average. NIOSH has
found that 25% of noise-exposed workers in Mining, Quarrying, and Oil
and Gas Extraction have hearing impairment. The prevalence of hearing loss increased by 1% from 1991-2001 within these workers.
Noise studies have been conducted in several mining environments.
Stageloaders (84-102 dBA), shearers (85-99 dBA), auxiliary fans (84–120
dBA), continuous mining machines (78–109 dBA), and roof bolters (92–103
dBA) represent some of the noisiest equipment in underground coal mines. Dragline
oilers, dozer operators, and welders using air arcing were occupations
with the highest noise exposures among surface coal miners. Coal mines had the highest hearing loss injury likelihood.
Proper ventilation, hearing protection, and spraying equipment with water are important safety practices in mines.
Records
Chuquicamata, Chile, site of the largest circumference and second deepest open pit copper mine in the world.
As of 2008, the deepest mine in the world is TauTona in Carletonville, South Africa, at 3.9 kilometres (2.4 mi), replacing the neighboring Savuka Mine in the North West Province of South Africa at 3,774 meters (12,382 ft). East Rand Mine in Boksburg, South Africa
briefly held the record at 3,585 meters (11,762 ft), and the first mine
declared the deepest in the world was also TauTona when it was at 3,581
meters (11,749 ft).
The Moab Khutsong gold mine in North West Province (South Africa)
has the world's longest winding steel wire rope, which is able to lower
workers to 3,054 meters (10,020 ft) in one uninterrupted four-minute
journey.
The deepest mine in Europe is the 16th shaft of the uranium mines in Příbram, Czech Republic, at 1,838 meters (6,030 ft), second is Bergwerk Saar in Saarland, Germany, at 1,750 meters (5,740 ft).
The deepest open-pit mine in the world is Bingham Canyon Mine in Bingham Canyon, Utah, United States, at over 1,200 meters (3,900 ft). The largest and second deepest open-pit copper mine in the world is Chuquicamata in northern Chile at 900 meters (3,000 ft), which annually produces 443,000 tons of copper and 20,000 tons of molybdenum.
The deepest open-pit mine with respect to sea level is Tagebau Hambach in Germany, where the base of the pit is 293 meters (961 ft) below sea level.
The largest underground mine is Kiirunavaara Mine in Kiruna, Sweden.
With 450 kilometres (280 mi) of roads, 40 million tonnes of annually
produced ore, and a depth of 1,270 meters (4,170 ft), it is also one of
the most modern underground mines. The deepest borehole in the world is Kola Superdeep Borehole, but this is connected to scientific drilling, not mining.
Metal reserves and recycling
During the 20th century, the variety of metals
used in society grew rapidly. Today, the development of major nations
such as China and India and advances in technologies are fueling an
ever-greater demand. The result is that metal mining activities are
expanding and more and more of the world's metal stocks are above ground
in use rather than below ground as unused reserves. An example is the
in-use stock of copper. Between 1932 and 1999, copper in use in the US rose from 73 kilograms (161 lb) to 238 kilograms (525 lb) per person.
95% of the energy used to make aluminum from bauxite ore is saved by using recycled material. However, levels of metals recycling are generally low. In 2010, the International Resource Panel, hosted by the United Nations Environment Program (UNEP), published reports on metal stocks that exist within society and their recycling rates.
The report's authors observed that the metal stocks in society
can serve as huge mines above ground. However, they warned that the
recycling rates of some rare metals used in applications such as mobile
phones, battery packs for hybrid cars, and fuel cells are so low that
unless future end-of-life recycling rates are dramatically stepped up
these critical metals will become unavailable for use in modern
technology.
As recycling rates are low and so much metal has already been extracted, some landfills now contain a higher concentrations of metal than mines themselves. This is especially true of aluminum, used in cans, and precious metals, found in discarded electronics.
Furthermore, waste after 15 years has still not broken down, so less
processing would be required when compared to mining ores. A study
undertaken by Cranfield University has found £360 million of metals
could be mined from just 4 landfill sites. There is also up to 20MJ/kg of energy in waste, potentially making the re-extraction more profitable. However, although the first landfill mine opened in Tel Aviv, Israel in 1953, little work has followed due to the abundance of accessible ores.
