Mining n

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Providing membership services to professionals and companies that do business in the area of mining and geological activities in the Northwest Territories. Mining North, Canada. 224 likes. The NWT & Nunavut Chamber of Mines has been the voice of the Northern mining and exploration industry since 1967. Coal mining news. Explore related Coal articles for more information on the Coal mining industry.
Mining news and commentary from around the globe. Daily updates on gold and commodity prices, exploration, mine development and mining company activities. Provides mining industry news and information to miners, suppliers, industry investors and others. Information resources of Australia's Mining Monthly, Australia's. Providing membership services to professionals and companies that do business in the area of mining and geological activities in the Northwest Territories. Mining North, Canada. 224 likes. The NWT & Nunavut Chamber of Mines has been the voice of the Northern mining and exploration industry since 1967. Coal mining news. Explore related Coal articles for more information on the Coal mining industry.

"Underground mining" redirects here. For other uses, see Underground mining (soft rock) and Underground mining (hard rock).

For other uses, see Mining (disambiguation).

Mining is the extraction of valuable minerals or other geological materials from the earth, usually from an orebody, lode, vein, seam, mining n, reef or placer deposits. These deposits form a mineralized package that is of economic interest to the miner.

Ores recovered by mining include metals, coal, oil shale, gemstones, mining n, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. Mining is mining n to obtain any material that cannot be grown through agricultural processes, or created artificially in a laboratory or factory, mining n. 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 im mining a proposed mine, extraction of the desired materials, mining n, and final reclamation of the land after the mine is closed.[citation needed]

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 mining n of metals recycling are generally low. Unless future end-of-life recycling rates are stepped up, mining n, 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[edit]

Prehistoric mining[edit]

Since the beginning of civilization, people have used stone, ceramics and, later, mining n, 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.[1] 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 (ca 4000–3000 BC). Other hard rocks mined gtx 650 ti bitcoin mining collected for axes included the greenstone of the Langdale axe mining n based in the English Lake District.

The oldest-known mine on archaeological record is the "Lion Cave" in Swaziland, mining n, which radiocarbon dating shows to be about 43,000 years old. At this site Paleolithic humans mined hematite to make the red pigmentochre.[2][3] Mines of a similar age in Hungary are believed qrk mining be sites where Neanderthals may have mined flint for weapons and tools.[4]

Ancient Egypt[edit]

Ancient Egyptians mined malachite at Maadi.[5] At first, Egyptians used the bright green malachite stones for ornamentations and pottery. Later, between 2613 and 2494 BC, mining n, large building projects required expeditions mining n to the area of Wadi Maghareh in order to secure minerals and other resources not available in Egypt itself.[6] Quarries for turquoise and copper were also found at Wadi Hammamat, Tura, mining n, Aswan and various other Nubian sites on the Sinai Peninsula and at Timna.[6]

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 mining n. One of the complexes is shown in one of the earliest coal and mining industry 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[edit]

Further information: Mining in Roman Britain

Mining in Europe has a very long history. Examples include the silver mines of Laurium, which helped support the Greek mining n state of Athens. Although they had over 20,000 slaves working them, mining n, their technology was essentially identical to their Bronze Age predecessors.[7] At other mines, such as on the island of Thassos, marble was quarried by the Parians after they arrived in the 7th Century BC.[8] 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.[9] 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 minehead by numerous aqueducts. The water was used for a variety of purposes, mining n, 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 landfill mining 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 jb mining aqueducts tapped local rivers and sluiced the deposits. Spain was one of the most important mining regions, mining n, but all regions of the Roman Empire were exploited. In Great Britain the natives had mined minerals for millennia,[10] but after the Roman conquest, mining n, the scale of the operations increased dramatically, as the Romans needed Britannia's resources, mining n, especially gold, mining n, 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, mining n, they penetrated the water table and dewatered the mines using several kinds of machines, mining n, especially mining n 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, mining n, and lifting water about 24 metres (79 ft). They were worked as treadmills with miners standing on the top slats, mining n. Many examples of such devices have been found in old Roman mines and some examples are now preserved in the British Museum mining n the National Museum of Wales.[11]

Medieval Europe[edit]

Main article: Mining and metallurgy in medieval Europe

Mining as an industry underwent dramatic changes in medieval Europe. The mining industry in the early Middle Mining n was mainly focused on the extraction of copper and iron, mining n. Other precious metals were also used, mainly for gilding or coinage. Initially, many metals were obtained through open-pit mining, and ore was mining n extracted from shallow depths, rather than through deep mine shafts. Around the 14th century, mining n growing use of weapons, armour, stirrups, and horseshoes greatly increased the demand for iron. Medieval knights, for example, mining n, were often laden with up to 100 pounds (45 kg) of plate or chain link armour in addition to swords, lances and other weapons.[12] The overwhelming dependency on iron for mining n purposes spurred iron production and extraction processes.

The silver crisis of 1465 occurred australia in mining all mines had reached depths at which the shafts could no longer be pumped dry with the available technology.[13] Although an increased use of bank notes, 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, mining n. On the continent, mining n, mining n deposits belonged to the crown, and this regalian mining t shirts 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. Mining equipment from germany had iron, zinc, copper, lead, and tin ores. Landlords who owned the mining technology metals and coal under their estates then had a strong inducement to extract these metals or to lease mining n deposits and collect royalties from mine operators. English, German, mining n Dutch capital combined to finance extraction and refining. Hundreds of German technicians and skilled mining n were brought over; in 1642 a colony of 4,000 foreigners mining n mining and smelting copper at Keswick in the northwestern mountains.[14]

Use of water power in the form of water mills was extensive. The water mills were employed in crushing ore, mining n, 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.[15] 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.[16] 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 mining rock salt same principles used for grain threshing.[17]

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 mining n 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[edit]

See also: Cultural achievements of pre-colonial Philippines

Mining in the Philippines began around 1000 BC. The early Filipinos worked various mines of gold, silver, copper and iron, mining n. 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.[18] 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.[18] 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.[18] The natives were also known for mining pool status 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[edit]

There are ancient, mining n, prehistoric copper mines along Lake Superior, and metallic copper was still found there, near the surface, in colonial times. [19][20][21]

Indigenous peoples availed themselves of this copper starting at least 5,000 years ago,"[19] and copper tools, arrowheads, and other artifacts that were part of mining n extensive native trade network have been discovered, mining n. In addition, obsidian, flint, and other minerals were mined, worked, and traded.[20] Early French explorers who encountered the sites[clarification needed] made no use of the metals due to the difficulties of transporting them,[20] mining n the copper was eventually traded throughout the continent along major river routes.

In the early colonial visual data mining of the Americas, "native gold mining n silver was quickly expropriated and sent back to Spain in fleets of gold- and silver-laden galleons,"[22] 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."[23][24]

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.[25] 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.[26] 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, mining n, 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.[21]

Modern period[edit]

In the early 20th century, the gold and silver mining bitcoins fpga to the western United States also stimulated mining for coal as mining n as base metals such jincheng anthracite coal mining copper, mining n, lead, and iron, mining n. Areas in modern Montana, mining n, Utah, Arizona, and later Alaska became predominate suppliers of copper to the world, mining n, which was increasingly demanding copper for electrical and households goods.[27] 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 mining n early 20th century with nickel, copper, and gold.[27]

Meanwhile, Australia experienced the Australian gold rushes and by the 1850s was mining n 40% of the world's gold, followed by the establishment mining n large mines such as the Mining n Morgan Mine, which ran for nearly a hundred years, Broken Hill ore deposit (one of the largest zinc-lead ore deposits), and the iron conference mining 2015 mines at Iron Knob. After declines in production, another boom in mining occurred in the 1960s. Now, mining n, in the early 21st century, Australia remains a major world mineral producer.[28]

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, mining n, have begun to increase in demand as a result of new technologies.

Mine development and lifecycle[edit]

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 mining n to a mathematical resource estimation to estimate the size and grade of the deposit.

This estimation is used to conduct a pre-feasibility study to determine the theoretical economics of the ore deposit. This mining n, early on, mining n, whether further investment in estimation and engineering studies mining n 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 mining n movement of ore and waste constitutes the mining process. Often more waste mining n ore is mined during the life of a mine, mining n, 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 mining n the ore begins and continues as long as the ground fall mining 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[edit]

Mining techniques can mining n divided into two common excavation types: surface mining and sub-surface (underground) mining. Today, surface mining is much more mining n, and produces, for example, mining n, 85% of minerals (excluding petroleum and natural gas) in the United States, including 98% of metallic ores.[29]

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, mining n, 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., mining n, potash, potassium chloride, mining n chloride, sodium sulfate, mining n, which dissolve in water. Some minerals, such as copper minerals and uranium oxide, mining n, require acid or carbonate solutions to dissolve.[30][31]

Surface mining[edit]

Main article: Surface mining

Surface mining is done by mining n (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, mining n, stone and clay;[32]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 mining n 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.[33] Landfill mining has been thought of as a solution to dealing with long-term methane emissions and local pollution[34]

Underground mining[edit]

Main articles: Underground mining (hard rock) and Underground mining (soft rock)

Sub-surface mining consists of digging tunnels or shafts into the earth to reach buried ore deposits. Ore, mining n, for processing, and waste rock, mining n, 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, mining n, 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, mining n, sub level caving, mining n, and block caving.

Highwall mining[edit]

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, mining n, the Pushbeam Transfer Mechanism (PTM) automatically inserts a 19.72-foot (6.01 m) long rectangular Pushbeam mining n Segment) into the center section of the machine between the Powerhead and the cutterhead, mining n. 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[edit]

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 mining n which frees the desired minerals from the waste gravel, mining n. The minerals are then concentrated using sluices or jigs.

Large drills are used to sink shafts, excavate stopes, mining n, 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, mining n, mills, reactors, roasters and other equipment to consolidate the mineral-rich ministry of mining afghanistan and extract the desired compounds and metals from the ore.

Processing[edit]

Main articles: Mineral processing and Extractive metallurgy

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, mining n, 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, mining n. Only minor shaking or washing may be necessary to disaggregate (unclump) the sands or mining n before processing. Processing of ore from a lode mine, mining n, 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 mining n 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 aluminium. Geometallurgy combines the geologic sciences with extractive metallurgy and mining.

Environmental effects[edit]

Main article: Environmental impact of mining

Environmental issues can include erosion, formation of sinkholes, loss of biodiversity, and contamination of soil, mining n, groundwater and surface water by chemicals from mining processes. In some cases, mining n, additional forest logging is done in the vicinity of mines to create space for the storage of the created debris and soil.[35] Contamination resulting what do we use coal mining for leakage of chemicals can also affect the health of the local population if not properly controlled.[36] Extreme examples of pollution from mining activities include coal fires, which can last for years or mining n 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), mining n, and environmental monitoring mining n operation and after closure. However, in some areas, particularly in the developing world, government mining orphaned blocks 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, mining n, and criteria for Socially responsible mining n. Mining companies have used this oversight from the financial sector to argue for some level of industry self-regulation.[37] 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.[38]

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 mining arkansas to "act as a catalyst" in an effort to improve social and environmental performance in the mining and metals industry internationally.[37] The mining industry has provided funding to various conservation groups, mining n, 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.[39]

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", mining n, involve short inspections, although they have been accused of lacking rigor[clarification needed].[37]:183–4 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.[37]:185–6

The purpose of a 2012 EPS PEAKS paper[40] was to provide evidence on policies managing ecological costs and maximise socio-economic benefits of mining using host country regulatory initiatives. It found existing literature suggesting mining n 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 mining pool logo with the companies, enacting land use mining n impact assessments, and incorporate specialised support and standards agencies.
  • Set in play transparency and community participation initiatives using the wealth accrued.

Waste[edit]

Ore mills generate large amounts of waste, called tailings. For example, 99 tons of mining n are generated per ton of copper,[41] 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.[42] (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, mining n. Tailings, which are usually produced as a slurry, are most commonly dumped into ponds made from naturally existing valleys.[43] These ponds are secured by impoundments (dams or embankment dams).[43] 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;[44] for example, in the Marcopper mining disaster at least geforce 9800 gtx mining million tons of tailings were released into a local river.[44] 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[45]. Subaqueous tailings disposal is another option.[43] The mining industry has argued that submarine tailings disposal (STD), which disposes of tailings in the sea, mining n ideal because it avoids the risks of tailings ponds; although the practice is illegal in the United States and Canada, mining n, it is used in the developing world.[46]

The waste is classified as either sterile or mineralised, with acid generating potential, and the movement and storage of this material forms a major part of the mine planning process. When the mineralised package is determined by an economic cut-off, the near-grade mining n 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, mining n, 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, mining n. 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.[44]

Renewable energy and mining[edit]

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.[47] Cost savings can reach up to 70%.[48]

Mining industry[edit]

Main articles: List of mines, List 980 mining mining companies, Category:Mining companies, and Category:Mining industry by country

Mining exists in many countries, mining n. London is known as the capital of global "mining houses" such as Rio Tinto Group, BHP Billiton, and Mining n American PLC.[49] The US mining industry is also large, mining n, but it is dominated by the coal and other mining n minerals (e.g., rock and sand), and various regulations have worked to reduce the significance mining n mining in the United States.[49] In 2007 the total market capitalization of mining companies was reported at US$962 billion, which compares to a total global pistol mining cap of publicly traded companies of about US$50 trillion in 2007.[50] In 2002, Chile and Peru were reportedly the major mining countries of South America.[51] 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.[52]Mining in Mining n is mining n significant part of that country's economy. In the developed world, mining in Australia, with BHP Billiton mining n 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.[53]

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, mining n 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 mining n on mining companies, mining n, 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.[49] Some have argued that below juniors there exists a substantial sector of illegitimate companies primarily focused on manipulating stock prices.[49]

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.[54] 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, mining n, 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.[55]

Corporate classifications[edit]

Mining companies can be classified based mining n 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 mining n $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 mining n US$50 million.[56]

Regulation and governance[edit]

New regulations and a process of legislative reforms aim to improve the harmonization and stability of the mining sector in mineral-rich countries.[57] 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.[58] 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 approahes which would also include disadvantaged communities, and work towards sustainable development even after mine closure (including transparency and revenue management). By the early mining n, community development issues and resettlements became mainstream mining n in World Bank mining projects.[58] Mining-industry expansion after mineral prices increased in 2003 and also potential fiscal revenues in those mining n 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[clarification needed] the environmental protection laws in developing countries, as well as voluntary efforts by mining companies to improve their environmental impact.[59]

In 2007 the Mining n Industries Transparency Initiative (EITI) was mainstreamed[clarification needed] in all countries cooperating with the World Bank in mining industry reform.[58] The EITI operates and was implemented with the support of the EITI multi-donor trust fund, managed by the World Bank.[60] The EITI aims to increase transparency in transactions between governments and companies in extractive industries[61] by monitoring the ruschrome mining pvt ltd and benefits between industries and recipient governments. The entrance process is voluntary mining n each country and is monitored by multiple stakeholders mining n governments, private companies and civil society representatives, mining n for disclosure and dissemination of the reconciliation report;[58] however, mining n, the competitive disadvantage of company-by company public report is for some of the businesses in Ghana at least, the main constraint.[62] Therefore, mining n, the outcome assessment in terms of failure or success of the new EITI regulation mining n not only "rest on the government's shoulders" but also on civil society and companies.[63]

On the other hand, implementation has issues; mining games digging 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,[64] causes other problems, like a avalon life mining of investment in other less lucrative sectors, mining n, 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, mining n, D.R. Congo, Guinea, Liberia and Sierra Leone – i.e. almost half of the mining countries implementing the EITI.[64] 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 mining n it to their needs), creates another risk of unsuccessful implementation. Public awareness increase, where government should act as a mining n between public and initiative for a successful outcome of the policy is an important element to be considered.[65]

World Bank[edit]

The World Bank has been involved in mining since 1955, mainly through grants from its International Bank for Reconstruction and Development, mining n, with the Bank's Multilateral Investment Guarantee Agency offering political risk insurance.[66] Between 1955 and 1990 it provided about $2 billion to fifty mining projects, broadly categorized as reform and rehabilitation, greenfield mine construction, mineral processing, mining n, technical assistance, mining n, and engineering. These projects have been criticized, particularly the Ferro Carajas project of Brazil, begun in 1981.[67] 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.[37]:20

In 1992 the World Bank began to push for privatization of government-owned mining companies with a new set of codes, mining n, beginning with its report The Strategy for African Mining. In 1997, mining n, Latin America's largest miner Companhia Vale do Rio Doce (CVRD) was privatized, mining n. 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

Sulfur miner with 90 kg of sulfur carried from the floor of the Ijen Volcano (2015)
Mastering data mining berry world active mining map
Gallery, mining n, 12th to 13th century, Germany
View showing miners’ clothes suspended by pulleys, also wash basins and ventilation system, Kirkland Lake, Ontario, 1936.
Mantrip used for transporting miners within an underground mine
Caterpillar Highwall Miner HW300 - Technology Bridging Underground and Open Pit Mining
A Bucyrus Erie 2570 dragline and CAT 797 haul truck at the North Antelope Rochelle opencut coal mine
Iron hydroxide precipitate stains a stream receiving acid drainage from surface coal mining.
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Mining | Britannica.com

Coal mining news. Explore related Coal articles for more information on the Coal mining industry. Mining definition, the act, process, or industry of extracting ores, coal, etc., from mines. See more. Mining: Mining, process of extracting useful minerals from the surface of the Earth, including the seas. A mineral, with a few exceptions, is an inorganic substance. InfoMine provides comprehensive information on mining, the mining industry, mining technology and mineral exploration. InfoMine categories include mining news, mining. Become the best Bitcoin miner and learn how to mine Bitcoins with the best Bitcoin mining hardware, software, pools and cloud mining. Start News Pool Cloud Software. Introduction. Mining is the process of adding transaction records to Bitcoin's public ledger of past transactions (and a "mining rig" is a colloquial metaphor for a.

Provides mining industry news and information to miners, suppliers, industry investors and others. Information resources of Australia's Mining Monthly, Australia's. Providing membership services to professionals and companies that do business in the area of mining and geological activities in the Northwest Territories. Mining North, Canada. 224 likes. The NWT & Nunavut Chamber of Mines has been the voice of the Northern mining and exploration industry since 1967.


Mining, process of extracting useful minerals from the surface of the Earth, including the seas. A mineral, with a few exceptions, is an inorganic substance occurring in nature that has a definite chemical composition and distinctive physical properties or molecular structure. (One organic substance, coal, is often discussed as a mineral as well.) Ore is a metalliferous mineral, or an aggregate of metalliferous minerals and gangue (associated rock of no economic value), that can be mined at a profit. Mineral deposit designates a natural occurrence of a useful mineral, while ore deposit denotes a mineral deposit of sufficient extent and concentration to invite exploitation.

When evaluating mineral deposits, it is extremely important to keep profit in mind. The total quantity of mineral in a given deposit is referred to as the mineral inventory, but only that quantity which can be mined at a profit is termed the ore reserve. As the selling price of the mineral rises or the extraction costs fall, the proportion of the mineral inventory classified as ore increases. Obviously, the opposite is also true, and a mine may cease production because (1) the mineral is exhausted or (2) the prices have dropped or costs risen so much that what was once ore is now only mineral.

History

Archaeological discoveries indicate that mining was conducted in prehistoric times. Apparently, the first mineral used was flint, which, because of its conchoidal fracturing pattern, could be broken into sharp-edged pieces that were useful as scrapers, knives, and arrowheads. During the Neolithic Period, or New Stone Age (about 8000–2000 bce), shafts up to 100 metres (330 feet) deep were sunk in soft chalk deposits in France and Britain in order to extract the flint pebbles found there. Other minerals, such as red ochre and the copper mineral malachite, were used as pigments. The oldest known underground mine in the world was sunk more than 40,000 years ago at Bomvu Ridge in the Ngwenya mountains, Swaziland, to mine ochre used in burial ceremonies and as body colouring.

Gold was one of the first metals utilized, being mined from streambeds of sand and gravel where it occurred as a pure metal because of its chemical stability. Although chemically less stable, copper occurs in native form and was probably the second metal discovered and used. Silver was also found in a pure state and at one time was valued more highly than gold.

According to historians, the Egyptians were mining copper on the Sinai Peninsula as long ago as 3000 bce, although some bronze (copper alloyed with tin) is dated as early as 3700 bce. Iron is dated as early as 2800 bce; Egyptian records of iron ore smelting date from 1300 bce. Found in the ancient ruins of Troy, lead was produced as early as 2500 bce.

One of the earliest evidences of building with quarried stone was the construction (2600 bce) of the great pyramids in Egypt, the largest of which (Khufu) is 236 metres (775 feet) along the base sides and contains approximately 2.3 million blocks of two types of limestone and red granite. The limestone is believed to have been quarried from across the Nile. Blocks weighing as much as 15,000 kg (33,000 pounds) were transported long distances and elevated into place, and they show precise cutting that resulted in fine-fitting masonry.

One of the most complete early treatments of mining methods in Europe is by the German scholar Georgius Agricola in his De re metallica (1556). He describes detailed methods of driving shafts and tunnels. Soft ore and rock were laboriously mined with a pick and harder ore with a pick and hammer, wedges, or heat (fire setting). Fire setting involved piling a heap of logs at the rock face and burning them. The heat weakened or fractured the rock because of thermal expansion or other processes, depending on the type of rock and ore. Crude ventilation and pumping systems were utilized where necessary. Hoisting up shafts and inclines was done with a windlass; haulage was in “trucks” and wheelbarrows. Timber support systems were employed in tunnels.

Great progress in mining was made when the secret of black powder reached the West, probably from China in the late Middle Ages. This was replaced as an explosive in the mid-19th century with dynamite, and since 1956 both ammonium nitrate fuel-blasting agents and slurries (mixtures of water, fuels, and oxidizers) have come into extensive use. A steel drill with a wedge point and a hammer were first used to drill holes for placement of explosives, which were then loaded into the holes and detonated to break the rock. Experience showed that proper placement of holes and firing order are important in obtaining maximum rock breakage in mines.

The invention of mechanical drills powered by compressed air (pneumatic hammers) increased markedly the capability to mine hard rock, decreasing the cost and time for excavation severalfold. It is reported that the Englishman Richard Trevithick invented a rotary steam-driven drill in 1813. Mechanical piston drills utilizing attached bits on drill rods and moving up and down like a piston in a cylinder date from 1843. In Germany in 1853 a drill that resembled modern air drills was invented. Piston drills were superseded by hammer drills run by compressed air, and their performance improved with better design and the availability of quality steel.

Developments in drilling were accompanied by improvements in loading methods, from handloading with shovels to various types of mechanical loaders. Haulage likewise evolved from human and animal portage to mine cars drawn by electric locomotives and conveyers and to rubber-tired vehicles of large capacity. Similar developments took place in surface mining, increasing the volume of production and lowering the cost of metallic and nonmetallic products drastically. Large stripping machines with excavating wheels used in surface coal mining are employed in other types of open-pit mines.

Water inflow was a very important problem in underground mining until James Watt invented the steam engine in the 18th century. After that, steam-driven pumps could be used to remove water from the deep mines of the day. Early lighting systems were of the open-flame type, consisting of candles or oil-wick lamps. In the latter type, coal oil, whale oil, or kerosene was burned. Beginning in the 1890s, flammable acetylene gas was generated by adding water to calcium carbide in the base of a lamp and then released through a jet in the centre of a bright metal reflector. A flint sparker made these so-called carbide lamps easy to light. In the 1930s battery-powered cap lamps began entering mines, and since then various improvements have been made in light intensity, battery life, and weight.

Although a great deal of mythic lore and romance has accumulated around miners and mining, in modern mining it is machines that provide the strength and trained miners who provide the brains needed to prevail in this highly competitive industry. Technology has developed to the point where gold is now mined underground at depths of 4,000 metres (about 13,100 feet), and the deepest surface mines have been excavated to more than 700 metres (about 2,300 feet).

George B. ClarkWilliam Andrew Hustrulid

Prospecting and exploration

Various techniques are used in the search for a mineral deposit, an activity called prospecting. Once a discovery has been made, the property containing a deposit, called the prospect, is explored to determine some of the more important characteristics of the deposit. Among these are its size, shape, orientation in space, and location with respect to the surface, as well as the mineral quality and quality distribution and the quantities of these different qualities.

Prospecting

In searching for valuable minerals, the traditional prospector relied primarily on the direct observation of mineralization in outcrops, sediments, and soil. Although direct observation is still widely practiced, the modern prospector also employs a combination of geologic, geophysical, and geochemical tools to provide indirect indications for reducing the search radius. The object of modern techniques is to find anomalies—i.e., differences between what is observed at a particular location and what would normally be expected. Aerial and satellite imagery provides one means of quickly examining large land areas and of identifying mineralizations that may be indicated by differences in geologic structure or in rock, soil, and vegetation type. In geophysical prospecting gravity, magnetic, electrical, seismic, and radiometric methods are used to distinguish such rock properties as density, magnetic susceptibility, natural remanent magnetization, electrical conductivity, dielectric permittivity, magnetic permeability, seismic wave velocity, and radioactive decay. In geochemical prospecting the search for anomalies is based on the systematic measurement of trace elements or chemically influenced properties. Samples of soils, lake sediments and water, glacial deposits, rocks, vegetation and humus, animal tissues, microorganisms, gases and air, and particulates are collected and tested so that unusual concentrations can be identified.

Exploration

On the basis of such studies, a number of prospects are identified. The most promising of these becomes the focus of a field exploration program. Several exploration techniques are used, depending on the type of deposit and its proximity to the surface. When the top of a deposit intersects the surface, or outcrops, shallow trenches may be excavated with a bulldozer or backhoe. Trenching provides accurate near-surface data and the possibility of collecting samples of large volume for testing. The technique is obviously limited to the cutting depth of the equipment involved. Sometimes special drifts are driven in order to explore a deposit, but this is a very expensive and time-consuming practice. In general, the purpose of driving such drifts is to provide drilling sites from which a large volume can be explored and a three-dimensional model of the potential ore body developed. Old shafts and drifts often provide a valuable and convenient way of sampling existing reserves and exploring extensions.

The most widely used exploration technique is the drilling of probe holes. In this practice a drill with a diamond-tipped bit cuts a narrow kerf of rock, extracting intact a cylindrical core of rock in the centre (seecore sampling). These core holes may be hundreds or even thousands of metres in length; the most common diameter is about 50 mm (2 inches). The cores are placed in special core boxes in the order in which they were removed from the hole. Geologists then carefully describe, or log, the core in order to determine the location and kinds of rock and mineral present; the different structural features such as joints, faults, and bedding planes; and the strength of the rock material. Cores are often split lengthwise, with one half being sent to a laboratory so that the grade, or content, of mineralization can be determined.

Delineation

Normally, core holes are drilled in a more or less regular pattern, and the locations of the holes are plotted on plan maps. In order to visualize how the deposit appears at depth, holes are also plotted along a series of vertical planes called sections. The geologist then examines each section and, on the basis of information collected from the maps and core logs as well as his knowledge of the structures present, fills in the regions lying between holes and between planes. This method of constructing an ore body is widely used where the boundaries between ore and waste are sharp and where medium to small deposits are mined by underground techniques, but, in the case of large deposits mined by open-pit methods, it has largely been replaced by the use of block models. These will be discussed in more detail below (seeSurface mining).

Mineral deposits have different shapes, depending on how they were deposited. The most common shape is tabular, with the mineral deposit lying as a filling between more or less parallel layers of rock. The orientation of such an ore body can be described by its dip (the angle that it makes with the horizontal) and its strike (the position it takes with respect to the four points of the compass). Rock lying above the ore body is called the hanging wall, and rock located below the ore body is called the footwall.

The concentration of a valuable mineral within an ore is often referred to as its grade. Grade may exhibit considerable variation throughout a deposit. Moreover, there is a certain grade below which it is not profitable to mine a mineral even though it is still present in the ore. This is called the mine cutoff grade. And, if the material has already been mined, there is a certain grade below which it is not profitable to process it; this is the mill cutoff grade. The grade at which the costs associated with mining and mineral processing just equal the revenues is called the break-even grade. Material having a higher grade than this would be considered ore, and anything below that would be waste.

Therefore, in determining which portion of a mineral can be considered an exploitable ore reserve, it is necessary to estimate extraction costs and the price that can be expected for the commodity. Extraction costs depend on the type of mining system selected, the level of mechanization, mine life, and many other factors. This makes selecting the best system for a given deposit a complex process. For example, deposits outcropping at the surface may initially be mined as open pits, but at a certain depth the decision to switch to underground mining may have to be made. Even then, the overall cost per ton of ore delivered to the processing plant would be significantly higher than from the open pit; to pay for these extra costs, the grade of the underground ore would have to be correspondingly higher.

Surface mining

It has been estimated that more than two-thirds of the world’s yearly mineral production is extracted by surface mining. There are several types of surface mining, but the three most common are open-pit mining, strip mining, and quarrying. These differ from one another in the mine geometries created, the techniques used, and the minerals produced.

Open-pit mining often (but not always) results in a large hole, or pit, being formed in the process of extracting a mineral. It can also result in a portion of a hilltop being removed. In strip mining a long, narrow strip of mineral is uncovered by a dragline, large shovel, or similar type of excavator. After the mineral has been removed, an adjacent strip is uncovered and its overlying waste material deposited in the excavation of the first strip. Since strip mining is primarily applied to thin, flat deposits of coal, it is not discussed here (seecoal mining).

There are two types of quarrying. There is the extraction of ornamental stone blocks of specific colour, size, shape, and quality—an operation requiring special and expensive production procedures. In addition, the term quarrying has been applied to the recovery of sand, gravel, and crushed stone for the production of road base, cement, concrete, and macadam. However, since the practices followed in these operations are similar to those of open-pit mines, the discussion of quarrying here is limited to the excavation of ornamental stone.

Open-pit mining

Pit geometry

Deposits mined by open-pit techniques are generally divided into horizontal layers called benches. The thickness (that is, the height) of the benches depends on the type of deposit, the mineral being mined, and the equipment being used; for large mines it is on the order of 12 to 15 metres (about 40 to 50 feet). Mining is generally conducted on a number of benches at any one time. The top of each bench is equivalent to a working level, and access to different levels is gained through a system of ramps. The width of a ramp depends on the equipment being used, but typical widths are from 20 to 40 metres (65 to 130 feet). Mining on a new level is begun by extending a ramp downward. This initial, or drop, cut is then progressively widened to form the new pit bottom.

The walls of a pit have a certain slope determined by the strength of the rock mass and other factors. The stability of these walls, and even of individual benches and groups of benches, is very important—particularly as the pit gets deeper. Increasing the pit slope angle by only a few degrees can decrease stripping costs tremendously or increase revenues through increased ore recovery, but it can also result in a number of slope failures on a small or large scale. Millions of tons of material may be involved in such slides. For this reason, mines have ongoing slope-stability programs involving the collection and analysis of structural data, hydrogeologic information, and operational practices (blasting, in particular), so that the best slope designs may be achieved. It is not unusual for five or more different slope angles to be involved in one large pit.

As a pit is deepened, more and more waste rock must be stripped away in order to uncover the ore. Eventually there comes a point where the revenue from the exposed ore is less than the costs involved in its recovery. Mining then ceases. The ratio of the amount of waste rock stripped to ore removed is called the overall stripping ratio. The break-even stripping ratio is a function of ore value and the costs involved.

Ore reserves

The first step in the evaluation and design of an open-pit mine is the determination of reserves. As was explained above, information regarding the deposit is collected through the drilling of probe holes. The locations of the holes are plotted on a plan map, and sections taken through the holes give a good idea of the ore body’s vertical extent. From these vertical sections the tentative locations of the benches are selected. However, since the deposit is to be mined in horizontal benches, it is also convenient to calculate the ore reserve in horizontal sections, with the thickness of each section equal to the height of a bench. These horizontal sections are divided along coordinate lines into a series of blocks, with the plan dimensions (i.e., the length and width) of each block generally being one to three times the bench height. After the grade of each block has been determined, the blocks are assembled into a block model representation of the ore body. (This model must be significantly larger than the actual ore reserve in order to include the eventual pit that must be dug to expose the ore body.)

Economic factors such as costs and expected revenues, which vary with grade and block location, are then applied; the result is an economic block model. Some of the blocks in the model will eventually fall within the pit, but others will lie outside. Of the several techniques for determining which of the blocks should be included in the final pit, the most common is the floating cone technique. In two dimensions the removal of a given ore block would require the removal of a set of overlying blocks as well. All of these would be included in an inverted triangle with its sides corresponding to the slope angle, its base lying on the surface, and its apex located in the ore block under consideration. In an actual three-dimensional case, this triangle would be a cone. The economic value of the ore block at the apex of the cone would be compared with the total cost of removing all of the blocks included in the cone. If the net value proved positive, then the cone would be mined. This technique would be applied to all of the blocks making up the block model, and at the end of this process a final pit outline would result.

Unit operations

The largest open-pit operations can move almost one million tons of material (both ore and waste) per day. In smaller operations the rate may be only a couple of thousand tons per day. In most of these mines there are four unit operations: drilling, blasting, loading, and hauling.

In large mines rotary drills are used to drill holes with diameters ranging from 150 to 450 mm (about 6 to 18 inches). The drill bit, made up of three cones containing either steel or tungsten carbide cutting edges, is rotated against the hole bottom under a heavy load, breaking the rock by compression and shear. An air compressor on the drilling machine forces air down the centre of the drill string so that the cuttings are removed. In smaller pits holes are often drilled by pneumatic or hydraulic percussion machines. These rigs may be truck- or crawler-mounted. Hole diameters are often in the range of 75 to 120 mm (about 3 to 5 inches).

Holes are drilled in special patterns so that blasting produces the types of fragmentation desired for the subsequent loading, hauling, and crushing operations. These patterns are defined by the burden (the shortest distance between the hole and the exposed bench face) and the spacing between the holes. Generally, the burden is 25 to 35 times the diameter of the blasthole, depending on the type of rock and explosive being used, and the spacing is equal to the burden.

There are a number of explosives used, but most are based on a slurry of ammonium nitrate and fuel oil (ANFO), which is transported by tanker truck and pumped into the holes. When filled with ANFO, a blasthole 400 mm (about 16 inches) in diameter and 7.5 metres (about 25 feet) deep can develop about one billion horsepower. It is incumbent upon those involved in the drilling and blasting to turn this power into useful fragmentation work. To achieve the proper fragmentation, a series of blastholes is generally shot in a carefully controlled sequence.

The object of blasting is to fragment the rock and then displace it into a pile that will facilitate its loading and transport. In large open pits the main implements for loading are electric, diesel-electric, or hydraulic shovels, while electric or mechanical-drive trucks are used for transport. The size of the shovels is generally specified by dipper, or bucket, size; those in common use have dipper capacities ranging from 15 to 50 cubic metres (20 to 65 cubic yards). This means that 30 to 100 tons can be dug in a single “bite” of the shovel. The size of the trucks is matched to that of the shovel, a common rule of thumb being that the truck should be filled in four to six swings of the shovel. Thus, for a shovel of 15-cubic-metre capacity, a truck having a capacity of 120 to 180 tons (four to six swings) should be assigned. The largest trucks have capacities of more than 350 tons (about 12 swings) and are equipped with engines that produce more than 3,500 horsepower; their tire diameters are often more than 3 metres (10 feet). Because of their high mobility, very large-capacity wheel loaders (front-end loaders) are also used in open-pit mines.

As pits became deeper—the deepest pits in the world exceed 800 metres (2,600 feet)—alternate modes of transporting broken ore and waste rock became more common. One of these is the belt conveyor, but in general this method requires in-pit crushing of the run-of-mine material prior to transport. For most materials a maximum angle of 18° is possible. To transport directly up the sides of pit walls, special conveying techniques are under development.

After loading, waste rock is transported to special dumps, while ore is generally hauled to a mineral-processing plant for further treatment. (In some cases ore is of sufficiently high quality for direct shipment without intermediate processing.) In some operations separate dumps are created for the various grades of sub-ore material, and these dumps may be re-mined later and processed in the mill. Certain dumps can be treated by various solutions to extract the contained metals (a process known as heap leaching or dump leaching).

Quarrying

Although seldom used to form entire structures, stone is greatly valued for its aesthetic appeal, durability, and ease of maintenance. The most popular types include granite, limestone, sandstone, marble, slate, gneiss, and serpentine. All natural stone used for structural support, curtain walls, veneer, floor tile, roofing, or strictly ornamental purposes is called building stone, and building stone that has been cut and finished for predetermined uses in building construction and monuments is known as dimension stone. The characteristics required of good dimension stone are uniformity of texture and colour, freedom from flaws, suitability for polishing and carving, and resistance to weathering. This section describes the quarrying of dimension stone.

Pit geometry

Although quarrying is also done underground, using room-and-pillar techniques, most quarries involve the removal of blocks from hillsides or from an open-pit type of geometry. The first step in developing such a quarry is the removal of the vegetative cover of trees and underbrush. Next, the overburden of topsoil and subsoil is removed and stockpiled for future reclamation. The rock is quarried in a series of benches or slices corresponding to the thickness of the desired blocks. This is often on the order of 4.5 to 6 metres (about 15 to 20 feet), but, since it is actual quarry practice to take advantage of any natural horizontal seams, block thickness may vary.

The quarrying process consists of separating large blocks, sometimes called loafs, from the surrounding rock. These blocks may be 6 metres high by 6 metres deep and 12 to 18 metres (about 40 to 60 feet) long, and they may weigh in the range of 1,200 to 2,000 tons. (Such large blocks are subsequently divided into mill blocks weighing 15 to 70 tons.) The removal of blocks from the quarry has traditionally been done by one or more fixed derricks. As a result, the plan area of a quarry has been determined not only by the geometry of the deposit and the amount of overburden but also by the reach of the derrick boom. However, derricks are gradually being replaced by highly mobile front-end loaders of sufficient capacity to move, lift, and carry 30-ton mill blocks, and the layout, design, and operating procedures of quarries are being modified accordingly.

There is a very high waste factor in the quarrying of dimension stone. For some quarries the amount of usable stone is only 15 to 20 percent of that quarried. For this reason an important aspect of quarry planning is the location of the waste or “grout” pile.

Unit operations

There are a number of techniques for separating a mass of stone from the parent mass. For many years the primary technique was the wire saw, which consists of a single-, double-, or triple-stranded helicoidal steel wire about 6 mm (0.2 inch) in diameter into which sand, aluminum oxide, silicon carbide, or other abrasive is fed in a water slurry. As the wire is pulled across the surface, a groove or channel is worn in the stone. Although the wire does not do the cutting itself (this is done by the abrasive), it does wear in the process so that the width of the cut continuously decreases. If the wire breaks prior to the completion of a cut, there will be great difficulty in beginning again; hence, the wire must be sufficiently long to complete the cut. In granite quarrying, a rule of thumb is that about 27 metres (about 89 feet) of wire are used for each square metre of stone that is cut (8 feet of wire per square foot). Completing a 6-metre-high by 9-metre- (30-foot-) long cut thus requires approximately 1,450 metres (about 4,800 feet) of wire; indeed, a typical wire saw setup may require 3 to 5 km (2 to 3 miles) of wire driven by an electric motor or diesel engine and directed around the quarry by a system of sheave wheels. A single wire may make several cuts at one time by suitable sheave direction.

The advantage of wire sawing is that it produces a smooth cut that minimizes later processing and does not damage adjacent rock. The technique has largely been superseded by others, however. In hard rocks such as granite that have a significant quartz content, channels may be cut by handheld or automated jet burners. A pressurized mixture of fuel oil and air or of fuel oil and oxygen is burned in a combustion chamber similar to a miniature rocket engine, producing a high-temperature, high-velocity flame. A channel 75 to 150 mm (3 to 6 inches) wide and up to 6 metres deep can be formed.

Another technique for cutting slots involves drilling a series of long parallel holes, using pneumatically or hydraulically powered percussion drills. In line drilling, closely spaced pilot holes may be drilled first and the intervening material then removed by reaming with a larger-diameter bit. Other arrangements using special guides are also available. For softer, less-abrasive rocks, the remaining rock web between holes may simply be chipped or broached out.

Rock between less closely spaced holes (125 to 250 mm [about 5 to 10 inches] apart) can be broken rather than removed. One technique for doing this involves the use of special explosives to exert a high gas pressure against the hole walls and thereby produce a crack along the firing line. A mechanical technique for accomplishing this is the use of feathers and wedges. Feathers are two half-round pieces of steel that are inserted into all of the holes forming a side of the block. The quarry worker works down the row, inserting a wedge between each pair of feathers and then tapping the wedges with a sledgehammer. This forces pressure from the wedge to the feathers so that eventually a crack line forms. This procedure is commonly followed to form the bottom of a block and for dividing large blocks into smaller blocks. In the latter case a line of small-diameter holes only a few centimetres deep is required. In addition, special cement grouts that expand during curing, as well as special hydraulic pressurization techniques, have also been used.

A relatively new development is the diamond wire saw. This consists of a 6-mm steel carrier cable on which diamond-impregnated beads and injection-molded plastic spacers are alternately fixed. The plastic spacers protect the cable against the abrasiveness of the rock and also maintain the diamond segments on the cable. Relatively clean water serves both as the flushing medium and to cool the wire. The initiation of a cut requires two boreholes 40 to 90 mm (1.6 to 3.5 inches) in diameter. One hole is drilled down from the upper corner of the block, and the other is drilled horizontally along the bottom to intersect the vertical hole. The wire is strung through the holes, and a driving mechanism supplies the power to move the wire and apply the proper tension. The diamond wire cut is very narrow (thus reducing waste), and it does not produce cracks or fissures in the stone. Moreover, once the saw is set up, an operator is not required.

Large chain saws, similar to those used for cutting trees but equipped with tungsten carbide or diamond-tipped cutters, are applicable to marbles, limestones, travertines, shales such as slate, and some types of sandstone. The chain, made up of removable links that carry the tool holders, rides in a channel with replaceable walls and bottom. The machine is self-propelled through a rack-and-pinion mechanism along modular track sections.

Channels may be cut in the stone by high-pressure jets of water with or without the addition of an abrasive substance. Water is forced through a small-diameter nozzle at extremely high velocity, creating new cracks and penetrating small natural cracks. In the process, thin layers of rock are sliced away. The advantages of water-jet channeling are that it cuts narrow, straight channels with very little noise and that it does not damage the wall surface.

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