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Mining

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Mining History
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During the mining process, precious mineral resources are extracted from the earth's surface or from underground. Therefore mining processes are usually classified as underground mining or surface mining. These mineral resources include ores that contain commercially valuable metals such as iron or aluminum; precious stones such as diamonds; building stones such as granites; and solid fuels, such as coal and oil shale.

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[edit] History

The very first attempt to extract minerals from the earth was carried out by prehistoric people who dug pits and tunnels to gather minerals that were used to create pigments and make tools and weapons. Mining of tin and copper occurred around 3500 B.C. To construct the large, monumental pyramids of Egypt, stone was quarried. Other ancient civilizations such as the Romans realized the wealth in mineral production and occupied the silver, gold, and lead mines from the countries they conquered. After the Roman Empire split in 400 A.D., advancements in mining were slow and almost non-existent for the next thousand years.[1]

Mining of coal and iron started in the 1400s in Europe, quickly spreading to countries like France, Germany, and Sweden. Across the globe in South America, the Inca were also mining metals to make tools, weapons, and jewelry. Perhaps the biggest development in mining took place in the 1500s when gunpowder was introduced for the first time in European mines to blast rock. By the 1700s, the use of gunpowder in mining became a widespread practice.[2]

It wasn’t until the 1700s that mining took place in North America. European settlers coming to America brought their knowledge with them. For example, one of the earliest mining operations in the U.S. was carried out by French explorers who mined lead and zinc in southwest Missouri. The mining of gold was quickly to follow in 1799 in North Carolina. The discovery of gold at a place called Sutter’s Mill spawned the infamous California Gold Rush in 1848. The Gold Rush brought mining as a viable industry to the forefront of North American frontier life and paved the way for the discovery of other materials such as lead, copper, and silver that could also be mined. The mining of coal as a fuel source was also undertaken in Pennsylvania around the same time. Perhaps the two largest minerals ever mined in North America that revolutionized the mining industry as a whole were coal and gold.[3]

Miners pose with mining equipment in Arizona mine

[edit] Coal Mining in North America

Coal mining evolved as an important industry in both the U.S. and Canada. Coal mining in both countries was particularly relevant at the turn of the century when coal served as the primary fuel source that would come to drive the industrial age. Historically, coal has been used for lighting and electricity, domestic heating, industrial energy, railroad fuel, steam engines, and other forms of transportation.

The first documented mining of coal was the removal of 50 tons in 1748.[4] In Canada, the first coalmine, a small-scale operation, opened at Grand Lake in 1639. By 1720, French soldiers opened a coalmine near Cow Bay in Cape Breton. The mine provided coal to the fortress at Louisbourg and eventually spread south to Boston and other American ports. Coal production in Nova Scotia spread exponentially and by 1820, a total of 21 collieries were in operation.[5]

Coal production quickly began in other provinces too as demand escalated. Commercial coal mining started in New Brunswick in 1825. Coal was also first mined on Vancouver Island in the mid-19th century in towns such as Nanaimo and Cumberland. As the track to the transcontinental railway was laid across B.C. and spread east into Alberta, more coalmines sprung up near Lethbridge, Banff, Drumheller, and Edmonton. The juxtaposition of coalmines adjacent to railway lines was common since coal was used as the primary source of railway fuel and steam engines.[6] Railway lines also supplied a means of transport for moving coal to other vicinities for use. By 1867 annual coal production peaked at three million tons. In 1911, Canada’s western provinces emerged as the leaders in the country’s coal production and to this day still turns out 95 percent of the country’s supply despite downturns in the market through the 1950s and 1960s.[7]

Levels in coal production globally typically correlate with the demand for its use. In the U.S., for example, coal production in some of the country's 38 states that once reportedly mined coal peaked decades ago, and in other states, has only recently been revived.[8]

By the 1950s, the use of coal was for domestic heating, industrial energy, and transportation. Eventually, however, these traditional markets for the use of coal switched over to the use of petroleum products like oil and gasoline. As a result, annual yields in coal production fell dramatically.[9]

[edit] Developments in Coal Mining

In the early years of coal mining, underground methods were deployed to access and mine coal. Coal was mined from seams that were reached through tunnels driven in the earth. A main tunnel would first be driven, and then smaller subsequent tunnels were branched off and driven outward from the main tunnel and ran parallel to coal seams. As mining underground progressed, a network of tunnels and such workings could be expanded for miles outwardly. The two most common methods for extracting coal in early coalmines in both North America and in Europe were longwall mining and room and pillar mining.

Gold panning was a common type of placer mining during the Gold Rush.
Tools and methods of mining coal were at first crude and rudimentary with most mining work being done by manually with picks and shovels. Once removed, the coal was placed into one-ton coal cars. Sometimes “pit ponies” hauled mined coal back up to the surface, other times it was hauled manually by miners. Other tools included hand augers and drills, used to bore holes to charge explosives. The explosives loosened the coal from the rock face and the excess rock was hauled away. Coalmines were cold, wet, and damp and posed dangerous risks. Miners in the early years did not have adequate protective clothing or safety equipment. Some of the risks of working in the underground coalmines were the threat of falling rock and breathing in toxic air that contained methane,[10] in addition to breathing in fine coal dust that often developed into a disease called “black lung.”[11] To counteract the poor ventilation and air quality in the coalmines, large ventilation fans were placed on the surface and used to draw the bad air out of the mine meanwhile minimizing the level of explosive gases to one that was safe.[12]

By the 1900s, substantial improvements led to the mechanization of coal mining. Miners were equipped with hard hats and steel-toed boots after World War II. The introduction of compressed air drills, coal-cutting machines, and later, conveyors and underground loaders also became important pieces of equipment in the mining of coal.[13] Technological advancements also meant that railways were soon replaced by electric powered loaders and conveyor belts in the hauling of coal out of the mine.

[edit] The Gold Rush in North America.  

The first significant Gold Rush in the United States was the Georgia Gold Rush in the Appalachian Mountains in 1829. The California Gold Rush followed in 1848 in the Sierra Nevada region and quickly spread with other successive Gold Rushes occurring in Western North American that moved gradually northwards up through British Columbia. The Fraser River Gold Rush occurred in 1858 and the Cariboo Gold Rush followed shortly thereafter in 1863. a[14] The Klondike Gold Rush was the largest gold rush to take place in Canada in the Yukon interior between 1897 to 1898. Around 100,000 potential prospectors, most Americans, made the trek to the Yukon gold fields by steam ship or on foot. Of those, only 30,000 made the journey. By the time the majority of miners made it to Dawson City, other miners had already staked out the best claims. Many of these miners dreamed of striking it rich in a time of great economic depression, though few ever did.[15]  

[edit] Developments in Gold Mining

Gold mining before the onset of mining machinery was mostly a surface mining operation out of an individual basis at first. Known as placer mining, a kind of opencast mining or open-pit mining, the process involved a miner buying a claim or paying for dirt and then removing layers of the overburden. The pay dirt was shaken off through a rocker box that enabled the removal of large stones and rocks. The remaining debris was then run through a sluice, a device that washed the pay dirt down through an angular trough. What remained afterwards was gold and black sand that could be panned by hand. Once gold deposits had been exhausted from the surface miners began to organize themselves into larger scale mining camps. This led to the extraction of gold downward into the earth’s subsurface. Large-scale companies that worked large tracts of land and employed many men eventually replaced individual gold miners and placer mining.[16]

[edit] Types/Processes

[edit] Surface Mining

Surface mining is the least expensive method of extracting minerals from the earth. Excavation of the surface area will be stepped, benched, or sloped, and reach depths up to 1,500 feet (460 m).[17] Most coal, for example, is extracted using this method.

In surface mining, material known as overburden is removed from the earth's surface so that the ore or coal bed can be extracted and then maintained afterward. The overburden can be removed through various methods such as strip mining and open-pit mining.

In strip mining, the soft overburden or waste soil overlying the ore or coal deposit is removed and put to the side. In this way, the excavated areas remain shallow, allowing the area to be re-contoured back to the pre-existing topography. Mountaintop mining is similar to strip mining in that overburden above a coal deposit is removed, but is then used to fill in adjacent valleys rather than restoring the existing topography.

Open-pit mining is a lot more labor intensive. Also known as open-cut mining, this method of extraction involves low-grade ore that is scattered sporadically throughout the existing rock bed instead of concentrated in a vein or pocket. Cuts or extractions are made in the earth's surface and remain open for the duration of the mine's life. The main objective with open-pit mining is to remove large amounts of rock at the lowest cost possible. Drilling and blasting the rock bed into reasonable sizes where it is then loaded and hauled away to a concentrator or treatment plant accomplish this. Open-pit mines can take decades to excavate, and re-contouring the landscape is not economically viable.

Alluvial mining is used to recover minerals such as gold from beds known as placer deposits. These deposits are removed mechanically by agitating the sand and gravel in simple pans or by separating the placer minerals from the sand and gravel using a sluice box.

Machinery involved in surface mining operations typically include excavators for digging up the dirt, wheel loaders for moving material, dump trucks (sometimes called "monster trucks") for hauling and moving materials, crawler tractors for pushing dirt around and fixing the land when a mine closes down, and motor graders for leveling the land for mining as well as fixing it after a mine closes.[18]

An opencast mine.

[edit] Underground Mining

If surface mining becomes too expensive of an operation, then underground mining is necessary. This involves the excavation of tunnels and rooms beneath the earth's surface to gain access to ore deposits that are usually of high value and concentrated in narrow views or unusually rich deposits.

One factor used in determining underground mining as an alternative to surface mining is strip-ratio, the number of units of waste material in a surface mine that must be removed to extract one unit of ore.[19] Once this number becomes too high, surface mining is no longer a viable option. With underground mining, the main objective is to remove the ore as economically and safely as possible without much waste.

Entry into the underground mine is typically through a range of entry points that include shafts, adits, inclines, and tunnels. Adits are horizontal passages constructed into a hillside, shafts are vertical tunnels constructed downward from the surface, and inclines are sloping passages excavated inward from a hill. The ore is typically mined in rooms with pillars that provide critical support to the roof and are made up of leftover material. A stope is an open room produced by the removal of ore in which mining is taking place. A vertical internal connection between two rooms or levels extending downward is referred to as a winze, and upward, a raise.

Underground mines can be excavated using a variety of methods. Room and pillar mining consists of intersecting rooms underground with pillars holding up the roof. The pillars are then mined when the mine or part of the mine is closing. The roof will cave in after the room and pillars have been mined. This method of mining is commonly used in coalmines.

Longwall mining entails using a piece of equipment called a continuous miner to slice coal or other layers of mineral from the room's walls.

Drift mining is when the mineral or rock to be mined is located on the side of the mountain and a horizontal opening is dug a little lower than the rock or mineral vein making retrieval easier and more affordable.

Shaft mining is the deepest form of underground mining. When rocks or minerals are too deep underground to reach through surface mining, a man shaft or tunnel is dug to the bottom of the mine and an elevator is used to transport workers and equipment. Smaller and shorter tunnels also branch off of the main shaft to reach the ore. The ore is dynamited to loosen it and then transported back to the surface through a secondary shaft and loaded into trucks. There is also an airshaft that provides ventilation.

Slope mining is when the coal or ore is located very deep and parallel to the ground. Shafts are drilled and dug out on a slant or slope because digging shafts straight down can pose problems or are too risky and dangerous.

Borehole mining is a hole typically bored deep into the ground to reach whatever rock or ore is going to be mined. A long tube-like tool is inserted into the hole. Water is forced down the tube and has places where the water can be pushed back up. The water combines the minerals, rock, and dirt together to create a slurry.[20] The slurry is pumped up back to the surface and kept in a large storage tank where the water is drained and the ore separated.

In hard rock mining, there is an opening called an adit, which is the point of entry into the underground mine. Tunnels, called shafts, are also blasted with dynamite or drilled vertical to the ground. These shafts have different purposes such as transporting workers or equipment or providing air ventilation. Tunnels are divided into many rooms with rock pillars resembling a sort of underground building with rooms upon rooms. When the miners decide to stop extracting coal or ore from the mine, they conduct something they call "robbing the pillars." Upon exiting the room, the coal is extracted from the pillars that hold up the roof and the room caves in. Hard rock mining is very dangerous because it takes place deep underground and miners can be exposed to deadly gases, cave-ins and explosions.

Machinery involved in underground mining operations involves more specialized equipment. Articulated dump trucks move large amounts of materials through the mine and can maneuver more easily than regular dump trucks. Longwall mining equipment is used to cut out long layers of coal from the walls and hold up the roof.  Shuttle cars were used to take coal or ore out of the mine, but now trucks are typically used.[21]

[edit] Equipment List

[edit] References

  1. Kroeger, Edwin Bane. Mining. World Book Online Reference Center, 2008.
  2. Kroeger, Edwin Bane. Mining. World Book Online Reference Center, 2008.
  3. Kroeger, Edwin Bane. Mining. World Book Online Reference Center, 2008.
  4. History of Coal Use. ByDesign.com, 2008-09-30.
  5. Coal: History in Canada. The Canadian Encyclopedia, 2008-09-30.
  6. Coal: History in Canada. The Canadian Encyclopedia, 2008-09-30.
  7. Coal: History in Canada. The Canadian Encyclopedia, 2008-09-30.
  8. History of Coal Use. ByDesign.com, 2008-09-30.
  9. Coal: History in Canada. The Canadian Encyclopedia, 2008-09-30.
  10. Mining Coal - Costs - Poisonous Gases. Sparwood Virtual Museum of Coal Mining, 2008-09-30.
  11. Mining Coal - Costs - Ventilation. Sparwood Virtual Museum of Coal Mining, 2008-09-30.
  12. Mining Coal - Costs - Ventilation. Sparwood Virtual Museum of Coal Mining, 2008-09-30.
  13. Mining Coal - Methods - History. Sparwood Virtual Museum of Coal Mining, 2008-09-30.
  14. History of gold mining. Kingsgate Consolidated Limited, 2008-09-30.
  15. Gold Rush. The Canadian Encyclopedia. 2008-11-25.
  16. History of gold mining. Kingsgate Consolidated Limited, 2008-09-30.
  17. Mining. HighBeam Encyclopedia, 2008-09-30.
  18. Mining Machinery. Library.Thinkquest.org, 2008-09-30.
  19. Mining. HighBeam Encyclopedia, 2008-09-30.
  20. Borehole Mining. Library.Thinkquest.org, 2008-09-30.
  21. Mining Machinery. Library.Thinkquest.org, 2008-09-30.