place of mining extracting

extraction of resources | geology

extraction of resources | geology

Mining is the extraction of valuable minerals or other geological materials from the earth from an orebody, lode, vein, seam, or reef, which forms the mineralized package of economic interest to the miner.

Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, dimension stone, rock salt, potash, gravel, and clay. Mining is required to obtain any material that cannot be grown through agricultural processes, or created artificially in a laboratory or factory. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.

Mining of stone and metal has been done since pre-historic times. Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials, and final reclamation of the land after the mine is closed.

The nature of mining processes creates a potential negative impact on the environment both during the mining operations and for years after the mine is closed. This impact has led most of the worlds nations to adopt regulations designed to moderate the negative effects of mining operations. Safety has long been a concern as well, and modern practices have improved safety in mines significantly.

The process of mining from discovery of an ore body through extraction of minerals and finally to returning the land to its natural state consists of several distinct steps. The first is discovery of the ore body, which is carried out through prospecting or exploration to find and then define the extent, location and value of the ore body. This leads to a mathematical resource estimation to estimate the size and grade of the deposit.

This estimation is used to conduct a pre-feasibility study to determine the theoretical economics of the ore deposit. This identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work. The next step is to conduct a feasibility study to evaluate the financial viability, the technical and financial risks, and the robustness of the project.

This is when the mining company makes the decision whether to develop the mine or to walk away from the project. This includes mine planning to evaluate the economically recoverable portion of the deposit, the metallurgy and ore recoverability, marketability and payability of the ore concentrates, engineering concerns, milling and infrastructure costs, finance and equity requirements, and an analysis of the proposed mine from the initial excavation all the way through to reclamation. The proportion of a deposit that is economically recoverable is dependent on the enrichment factor of the ore in the area.

To gain access to the mineral deposit within an area it is often necessary to mine through or remove waste material which is not of immediate interest to the miner. The total movement of ore and waste constitutes the mining process. Often more waste than ore is mined during the life of a mine, depending on the nature and location of the ore body. Waste removal and placement is a major cost to the mining operator, so a detailed characterization of the waste material forms an essential part of the geological exploration program for a mining operation.

Once the analysis determines a given ore body is worth recovering, development begins to create access to the ore body. The mine buildings and processing plants are built, and any necessary equipment is obtained. The operation of the mine to recover the ore begins and continues as long as the company operating the mine finds it economical to do so. Once all the ore that the mine can produce profitably is recovered, reclamation begins to make the land used by the mine suitable for future use.

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

Targets are divided into two general categories of materials: placer deposits, consisting of valuable minerals contained within river gravels, beach sands, and other unconsolidated materials; and lode deposits, where valuable minerals are found in veins, in layers, or in mineral grains generally distributed throughout a mass of actual rock. Both types of ore deposit, placer or lode, are mined by both surface and underground methods.

Some mining, including much of the rare earth elements and uranium mining, is done by less-common methods, such as in-situ leaching: this technique involves digging neither at the surface nor underground. The extraction of target minerals by this technique requires that they be soluble, e.g., potash, potassium chloride, sodium chloride, sodium sulfate, which dissolve in water. Some minerals, such as copper minerals and uranium oxide, require acid or carbonate solutions to dissolve.

Surface mining is done by removing (stripping) surface vegetation, dirt, and, if necessary, layers of bedrock in order to reach buried ore deposits. Techniques of surface mining include: open-pit mining, which is the recovery of materials from an open pit in the ground, quarrying or gathering building materials from an open-pit mine; strip mining, which consists of stripping surface layers off to reveal ore/seams underneath; and mountaintop removal, commonly associated with coal mining, which involves taking the top of a mountain off to reach ore deposits at depth. Most (but not all) placer deposits, because of their shallowly buried nature, are mined by surface methods. Finally, landfill mining involves sites where landfills are excavated and processed.

This form of mining differs from extractive methods that require tunneling into the earth, such as long wall mining. Open-pit mines are used when deposits of commercially useful minerals or rocks are found near the surface; that is, where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunneling (as would be the case for sand, cinder, and gravel). For minerals that occur deep below the surfacewhere the overburden is thick or the mineral occurs as veins in hard rockunderground mining methods extract the valued material.

Open-pit mines are typically enlarged until either the mineral resource is exhausted, or an increasing ratio of overburden to ore makes further mining uneconomic. When this occurs, the exhausted mines are sometimes converted to landfills for disposal of solid wastes. However, some form of water control is usually required to keep the mine pit from becoming a lake, if the mine is situated in a climate of considerable precipitation or if any layers of the pit forming the mine border productive aquifers.

Open-cast mines are dug on benches, which describe vertical levels of the hole. These benches are usually on four to sixty meter intervals, depending on the size of the machinery that is being used. Many quarries do not use benches, as they are usually shallow.

Most walls of the pit are generally dug on an angle less than vertical, to prevent and minimize damage and danger from rock falls. This depends on how weathered the rocks are, and the type of rock, and also how many structural weaknesses occur within the rocks, such as a faults, shears, joints orfoliations.

The walls are stepped. The inclined section of the wall is known as the batter, and the flat part of the step is known as the bench or berm. The steps in the walls help prevent rock falls continuing down the entire face of the wall. In some instances additional ground support is required and rock bolts, cable bolts and shotcrete are used. De-watering bores may be used to relieve water pressure by drilling horizontally into the wall, which is often enough to cause failures in the wall by itself.

Ore which has been processed is known as tailings, and is generally a slurry. This is pumped to a tailings dam or settling pond, where the water evaporates. Tailings dams can often be toxic due to the presence of unextracted sulfide minerals, some forms of toxic minerals in the gangue, and oftencyanide which is used to treat gold ore via the cyanide leach process. This toxicity can harm the surrounding environment.

Gold is generally extracted in open-pit mines at 1 to 2ppm (parts per million) but in certain cases, 0.75ppm gold is economical. This was achieved by bulk heap leaching at the Peak Hill mine in western New South Wales, near Dubbo, Australia.

Nickel, generally as laterite, is extracted via open-pit down to 0.2%. Copper is extracted at grades as low as 0.15% to 0.2%, generally in massive open-pit mines in Chile, where the size of the resources and favorable metallurgy allows economies of scale.

Sub-surface mining consists of digging tunnels or shafts into the earth to reach buried ore deposits. Ore, for processing, and waste rock, for disposal, are brought to the surface through the tunnels and shafts. Sub-surface mining can be classified by the type of access shafts used, the extraction method or the technique used to reach the mineral deposit. Drift mining utilizes horizontal access tunnels, slope mining uses diagonally sloping access shafts, and shaft mining utilizes vertical access shafts. Mining in hard and soft rock formations require different techniques.

Other methods include shrinkage stope mining, which is mining upward, creating a sloping underground room, long wall mining, which is grinding a long ore surface underground, and room and pillar mining, which is removing ore from rooms while leaving pillars in place to support the roof of the room. Room and pillar mining often leads to retreat mining, in which supporting pillars are removed as miners retreat, allowing the room to cave in, thereby loosening more ore. Additional sub-surface mining methods include hard rock mining, which is mining of hard rock (igneous, metamorphic or sedimentary) materials, bore hole mining, drift and fill mining, long hole slope mining, sub level caving, and block caving.

Heavy machinery is used in mining to explore and develop sites, to remove and stockpile overburden, to break and remove rocks of various hardness and toughness, to process the ore, and to carry out reclamation projects after the mine is closed. Bulldozers, drills, explosives and trucks are all necessary for excavating the land. In the case of placer mining, unconsolidated gravel, or alluvium, is fed into machinery consisting of a hopper and a shaking screen or trommel which frees the desired minerals from the waste gravel. The minerals are then concentrated using sluices or jigs.

Large drills are used to sink shafts, excavate stopes, and obtain samples for analysis. Trams are used to transport miners, minerals and waste. Lifts carry miners into and out of mines, and move rock and ore out, and machinery in and out, of underground mines. Huge trucks, shovels and cranes are employed in surface mining to move large quantities of overburden and ore. Processing plants utilize large crushers, mills, reactors, roasters and other equipment to consolidate the mineral-rich material and extract the desired compounds and metals from the ore.

Once the mineral is extracted, it is often then processed. The science of extractive metallurgy is a specialized area in the science of metallurgy that studies the extraction of valuable metals from their ores, especially through chemical or mechanical means.

Mineral processing (or mineral dressing) is a specialized area in the science of metallurgy that studies the mechanical means of crushing, grinding, and washing that enable the separation (extractive metallurgy) of valuable metals or minerals from their gangue (waste material). Processing of placer ore material consists of gravity-dependent methods of separation, such as sluice boxes. Only minor shaking or washing may be necessary to disaggregate (unclump) the sands or gravels before processing. Processing of ore from a lode mine, whether it is a surface or subsurface mine, requires that the rock ore be crushed and pulverized before extraction of the valuable minerals begins. After lode ore is crushed, recovery of the valuable minerals is done by one, or a combination of several, mechanical and chemical techniques.

Since most metals are present in ores as oxides or sulfides, the metal needs to be reduced to its metallic form. This can be accomplished through chemical means such as smelting or through electrolytic reduction, as in the case of aluminium. Geometallurgy combines the geologic sciences with extractive metallurgy and mining.

Mining exists in many countries. London is known as the capital of global mining houses such as Rio Tinto Group, BHP Billiton, and Anglo American PLC.The US mining industry is also large, but it is dominated by the coal and other nonmetal minerals (e.g., rock and sand), and various regulations have worked to reduce the significance of mining in the United States.In 2007 the totalmarket capitalization of mining companies was reported at US$962 billion, which compares to a total global market cap of publicly traded companies of about US$50 trillion in 2007.In 2002, Chile and Peru were reportedly the major mining countries of South America.The mineral industry of Africa includes the mining of various minerals; it produces relatively little of the industrial metals copper, lead, and zinc, but according to one estimate has as a percent of world reserves 40% of gold, 60% of cobalt, and 90% of the worlds platinum group metals.Mining in India is a significant part of that countrys economy. In the developed world, mining in Australia, with BHP Billiton founded and headquartered in the country, and mining in Canada are particularly significant. For rare earth minerals mining, China reportedly controlled 95% of production in 2013.

Mining operations can be grouped into five major categories in terms of their respective resources. These are oil and gas extraction, coal mining, metal ore mining, nonmetallic mineral mining and quarrying, and mining support activities.Of all of these categories, oil and gas extraction remains one of the largest in terms of its global economic importance. Prospecting potential mining sites, a vital area of concern for the mining industry, is now done using sophisticated new technologies such as seismic prospecting and remote-sensing satellites. Mining is heavily affected by the prices of the commodity minerals, which are often volatile. The 2000s commodities boom (commodities supercycle) increased the prices of commodities, driving aggressive mining. In addition, the price of gold increased dramatically in the 2000s, which increasedgold mining; for example, one study found that conversion of forest in the Amazon increased six-fold from the period 20032006 (292 ha/yr) to the period 20062009 (1,915 ha/yr), largely due to artisanal mining.

Safety has long been a concern in the mining business especially in sub-surface mining. The Courrires mine disaster, Europes worst mining accident, involved the death of 1,099 miners in Northern France on March 10, 1906. This disaster was surpassed only by the Benxihu Colliery accident in China on April 26, 1942, which killed 1,549 miners.While mining today is substantially safer than it was in previous decades, mining accidents still occur. Government figures indicate that 5,000 Chinese miners die in accidents each year, while other reports have suggested a figure as high as 20,000.Mining accidents continue worldwide, including accidents causing dozens of fatalities at a time such as the 2007 Ulyanovskaya Mine disaster in Russia, the2009 Heilongjiang mine explosion in China, and the 2010 Upper Big Branch Mine disaster in the United States.

Mining ventilation is a significant safety concern for many miners. Poor ventilation inside sub-surface mines causes exposure to harmful gases, heat, and dust, which can cause illness, injury, and death. The concentration of methane and other airborne contaminants underground can generally be controlled by dilution (ventilation), capture before entering the host air stream (methane drainage), or isolation (seals and stoppings).Rock dusts, including coal dust and silicon dust, can cause long-term lung problems including silicosis, asbestosis, and pneumoconiosis (also known as miners lung or black lungdisease). A ventilation system is set up to force a stream of air through the working areas of the mine. The air circulation necessary for effective ventilation of a mine is generated by one or more large mine fans, usually located above ground. Air flows in one direction only, making circuits through the mine such that each main work area constantly receives a supply of fresh air. Watering down in coal mines also helps to keep dust levels down: by spraying the machine with water and filtering the dust-laden water with a scrubber fan, miners can successfully trap the dust.

Gases in mines can poison the workers or displace the oxygen in the mine, causing asphyxiation.For this reason, the U.S. Mine Safety and Health Administration requires that groups of miners in the United States carry gas detection equipment that can detect common gases, such as CO, O2, H2S, CH4, as well as calculate% Lower Explosive Limit. Regulation requires that all production stop if there is a concentration of 1.4% of flammable gas present. Additionally, further regulation is being requested for more gas detection as newer technology such as nanotechnology is introduced.

Ignited methane gas is a common source of explosions in coal mines, which in turn can initiate more extensive coal dust explosions. For this reason, rock dusts such as limestone dust are spread throughout coal mines to diminish the chances of coal dust explosions as well as to limit the extent of potential explosions, in a process known as rock dusting. Coal dust explosions can also begin independently of methane gas explosions. Frictional heat and sparks generated by mining equipment can ignite both methane gas and coal dust. For this reason, water is often used to cool rock-cutting sites.

Miners utilize equipment strong enough to break through extremely hard layers of the Earths crust. This equipment, combined with the closed work space in which underground miners work, can cause hearing loss.For example, a roof bolter (commonly used by mine roof bolter operators) can reach sound power levels of up to 115dB.Combined with the reverberant effects of underground mines, a miner without proper hearing protection is at a high risk forhearing loss.By age 50, nearly 90% of U.S. coal miners have some hearing loss, compared to only 10% among workers not exposed to loud noises.Roof bolters are among the loudest machines, but auger miners, bulldozers, continuous mining machines, front end loaders, and shuttle cars and trucks are also among those machines most responsible for excessive noise in mine work.

Since mining entails removing dirt and rock from its natural location, thereby creating large empty pits, rooms, and tunnels, cave-ins as well as ground and rock falls are a major concern within mines. Modern techniques for timbering and bracing walls and ceilings within sub-surface mines have reduced the number of fatalities due to cave-ins, but ground falls continue to represent up to 50% of mining fatalities.Even in cases where mine collapses are not instantly fatal, they can trap mine workers deep underground. Cases such as these often lead to high-profile rescue efforts, such as when 33 Chilean miners were trapped deep underground for 69 days in 2010.

High temperatures and humidity may result in heat-related illnesses, including heat stroke, which can be fatal. The presence of heavy equipment in confined spaces also poses a risk to miners. To improve the safety of mine workers, modern mines use automation and remote operation including, for example, such equipment as automated loaders and remotely operated rockbreakers. However, despite modern improvements to safety practices, mining remains a dangerous occupation throughout the world.

Environmental issues can include erosion, formation of sinkholes, loss of biodiversity, and contamination of soil, groundwater and surface water by chemicals from mining processes. In some cases, additional forest logging is done in the vicinity of mines to create space for the storage of the created debris and soil.Contamination resulting from leakage of chemicals can also affect the health of the local population if not properly controlled.Extreme examples of pollution from mining activities include coal fires, which can last for years or even decades, producing massive amounts of environmental damage.

Mining companies in most countries are required to follow stringent environmental and rehabilitation codes in order to minimize environmental impact and avoid impacting human health. These codes and regulations all require the common steps of environmental impact assessment, development of environmental management plans, mine closure planning (which must be done before the start of mining operations), and environmental monitoring during operation and after closure. However, in some areas, particularly in the developing world, government regulations may not be well enforced.

Ore mills generate large amounts of waste, called tailings. For example, 99 tons of waste are generated per ton of copper, with even higher ratios in gold mining. These tailings can be toxic. Tailings, which are usually produced as a slurry, are most commonly dumped into ponds made from naturally existing valleys.These ponds are secured by impoundments (dams orembankment dams).In 2000 it was estimated that 3,500 tailings impoundments existed, and that every year, 2 to 5 major failures and 35 minor failures occurred;for example, in the Marcopper mining disaster at least 2 million tons of tailings were released into a local river.Subaqueous tailings disposal is another option.The mining industry has argued that submarine tailings disposal (STD), which disposes of tailings in the sea, is ideal because it avoids the risks of tailings ponds; although the practice is illegal in the United States and Canada, it is used in the developing world.

The waste is classified as either sterile or 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 mineralised waste is usually dumped separately with view to later treatment should market conditions change and it becomes economically viable. Civil engineering design parameters are used in the design of the waste dumps, and special conditions apply to high-rainfall areas and to seismically active areas. Waste dump designs must meet all regulatory requirements of the country in whose jurisdiction the mine is located. It is also common practice to rehabilitate dumps to an internationally acceptable standard, which in some cases means that higher standards than the local regulatory standard are applied.

After mining finishes, the mine area must undergo rehabilitation. Waste dumps are contoured to flatten them out, to further stabilise them. If the ore contains sulfides it is usually covered with a layer of clay to prevent access of rain and oxygen from the air, which can oxidise the sulfides to producesulfuric acid, a phenomenon known as acid mine drainage. This is then generally covered with soil, and vegetation is planted to help consolidate the material. Eventually this layer will erode, but it is generally hoped that the rate of leaching or acid will be slowed by the cover such that the environment can handle the load of acid and associated heavy metals. There are no long term studies on the success of these covers due to the relatively short time in which large scale open pit mining has existed. It may take hundreds to thousands of years for some waste dumps to become acid neutral and stop leaching to the environment. The dumps are usually fenced off to prevent livestock denuding them of vegetation. The open pit is then surrounded with afence, to prevent access, and it generally eventually fills up with ground water. In arid areas it may not fill due to deep groundwater levels.

During the twentieth century, the variety of metals used in society grew rapidly. Today, the development of major nations such as China and India and advances in technologies are fueling an ever greater demand. The result is that metal mining activities are expanding and more and more of the worlds metal stocks are above ground in use rather than below ground as unused reserves. An example is the in-use stock of copper. Between 1932 and 1999, copper in use in the USA rose from 73 kilograms (161lb) to 238 kilograms (525lb) per person.

95% of the energy used to make aluminum from bauxite ore is saved by using recycled material.However, levels of metals recycling are generally low. In 2010, the International Resource Panel, hosted by the United Nations Environment Programme (UNEP), published reports on metal stocks that exist within societyand their recycling rates.

The reports authors observed that the metal stocks in society can serve as huge mines above ground. However, they warned that the recycling rates of some rare metals used in applications such as mobile phones, battery packs for hybrid cars, and fuel cells are so low that unless future end-of-life recycling rates are dramatically stepped up these critical metals will become unavailable for use in modern technology.

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the environmental impact of mining (different mining methods compared) | get green now

the environmental impact of mining (different mining methods compared) | get green now

Mining remains an essential and growing part of the modern industry. By some estimates, itmakes up nearly 45%of the total global economy, and mineral production continues to increase as demand for raw materials grows around the world.

Ore dust and gases released by the mining process are bad for the health of miners as well as the environment. Over time, exposure to the dust created by mining operations can lead to disease and buildup of scar tissue in the lungs.

Materials left over by the mining process can easily make their way into local water systems, leading to increased acidity and heavy metal contamination that can destroy wildlife and render water undrinkable.

Some forms of mining also require the draining of underground water reservoirs called aquifers, which can cause serious impacts like drying up springs, cutting off rivers and degrading local ecosystems.

Pit mining, one of the most common techniques, hollows out land to extract raw materials. It blasts away land and strips vegetation, leaving the area vulnerable to soil erosion the wearing away of the topsoil layer of time. Topsoil is necessary for plants to grow, and without it, mining sites cant truly recover.

All these different effects add up to serious on-site habitat damage. Mining also creates knock-on effects like water pollution, air pollution and vegetation loss as a result of soil eruption. This can lead to greater habitat loss beyond the immediate location.

The land left behind, if not rehabilitated, is typically vulnerable to further soil erosion, further scattering what little topsoil was left over. Its often not suitable for plant or animal life. Without human intervention, it may take years or decades for the land to become usable again.

Underground mining, where miners tunnel beneath the Earths surface to extract mineral deposits, is rarer than open-pit mining. In 2014, itmade up about 5%of all American mining operations and has less of an impact on the surface.

With this mining method, rocks and minerals are brought to the surface from tunnels underground. There, toxic chemicals in the waste material can escape into the environment and local waterways if not properly disposed of.

Underground mines can also cause subsidence on the surface the land above begins to sink, usually when underground supports fail in abandoned or inactive mines. This can shift buildings, destroy infrastructure and harm the surface environment.

Underground mining can also sometimes lower the water table. If miners need to dig through an aquifer or water-laden layer of earth, water will need to be pumped out of the mine for work to continue. This dewatering can dry up springs, cut off rivers and degrade local ecosystems.

Some mining techniqueslike in-situ leaching, which uses acid and water to remove minerals from a site without significantly disturbing the surface have much less environmental impact. In-situ mining techniques can use less water than open-pit mining and underground mining, and also reduce the risk of releasing ore dust into the atmosphere.

However, even low-impact mining techniques like in-situ mining arent consequence-free. The strong acids used to break down ore and rocks can result in acidification of the surrounding environment. The acids can also dissolve the metal and radioactive isotopes in these ores during the leaching process, both of which can find their way into nearby water sources.

Ore residue and acid leach heaps left by mining processes can also erode rock and eventually pollute waterways. At the Holden Mine Superfund Site, for example, more than 100 million metric tons of leftover materials are currently at risk of leaching into the Columbia River.

The company that owns the mine invested in a remediation wall to prevent these toxic waste materials from leaching into the river, but the wall isnt a permanent solution. Severe flooding could easily wash the waste elements into waterways, meaning the site will likely require further rehabilitation.

Plastic and rubber left by equipment like earth-mover tires will stick around if not directly addressed. This can pose other problems, too like the air pollution created as a result of diesel-burning engines.

Whats more, even though rehabilitation can prevent the effects of mining from getting worse over time, not all companies invest in rehabilitating their sites. As a result, many are left alone to pollute the nearby environment for years or even decades to come.

Companies may move in the direction of sustainability especially as pressure from individuals and governments push them to comply with higher standards ofenvironmental and social governance (ESG). Expert leaders on ESGand industry professionals from within miningpredict operations will begin to think more seriously about sustainability.

With the use of biosolids nutrient-rich organics derived from sewage treatment processes that are often used as soil conditioners in agriculture it may be possible to reintroduce plant life to former mining sites in as few as 12 weeks.

Other, even more ambitious rehabilitation plans are focused on the best possible stewardship of former mining sites. These plans look to not only rehabilitate the land, but also aim to reintroduce 100%of the species that were living there before operations began.

Machines with electric engines are becoming increasingly popular, with some companies, like Swedish mining equipment manufacturer Epiroc, even going so far as to pledge using100% electric products over the next few years. Widespread adoption of electric engines could easily help the industry reduce the amount of carbon dioxide it naturally produces.

Low-impact mining techniques are also becoming more popular. In-situ mining is seeing bigger use in countries like China, which is trying to grapple withgrowing mineral demand,the size of the mining industry and the significant impact on the environment.

Social changes from outside the industry may also naturally reduce minings carbon footprint over time and encourage more environmentally friendly techniques. For example, as businessesturn away from nonrenewable resources, mining may naturally follow suit.

This is troubling for those who care about the environment. Mining can often be devastating causing water acidification, soil erosion and the degradation of local ecosystems. While some methods have less impact than others, it almost always has a serious and lasting environmental impact.

Fortunately, there is some hope that mining will become more sustainable in the future. The adoption of low-impact techniques and more eco-friendly equipment plus pressure from environmentally minded individuals and governments may make the industry more eco-friendly over time.

Jenna is a tech journalist who co-ownsThe Byte Beatand frequently writes about the latest news in technology, disruptive tech, and environmental science and more. Check out her work on TBB or follow her on [email protected]_tsui!

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Thousands of toxic waste sites exist in the U.S as a consequence of improper waste disposal, resulting in the pollution and poisoning of lands for years to come. These heavily contaminated sites can include abandoned mines, industrial sites, landfills, waste dumps, and more. During the 1970s, infamous toxic dump sites such as Love Canal and

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in-situ recoverya move towards 'keyhole mining' - mining3

in-situ recoverya move towards 'keyhole mining' - mining3

Human demand for travel; metal structures and their accompanying heating, cooling and lighting; and luxuries (or rather, necessities) of mobile phones and laptops has contributed to the estimated consumption of almost 0.5 million kilograms of rocks, metals, and fuels per person per lifetime. Approximately 15 different minerals are required to make a car, 30 minerals are required to make a computer and as many as 42 different minerals are required to make a phone. The bottom line is, we will continue to require metals, and while recycling will continue to grow in importance, mining will remain the primary avenue to obtaining these metals. The acquisition of these metals requires significant investment and effort, mostly in the form of underground and surface mines to extract the desired metals or minerals, and subsequent processing. However, current mining processes face a number of challenges related directly to the deposit itself, challenges that are linked to technical processing limitations and economics, and increasingly, challenges that are related to licence to operate (environmental, societal approval etc.) and sustainability (power, water, waste etc.).

Besides uncertain commodity prices that make the prediction of value difficult, ore deposits are becoming lower in grade (Fig. 1), with increasingly challenging mineralogies, difficult mineralisations and problematic gangue minerals or impurities. Their progressively greater depths incur greater mining costs and require higher strip ratios, resulting in increased amounts of waste and water usage.

Many deposits are located remotely with limited infrastructure, which incurs challenges in terms of logistics, including the provision of a workforce or skilled employees and essential services such as energy and water. Some may be located in protected areas where regulations and licence to operate are ever harder to obtain. Capital and operating costs may render a deposit uneconomical, and of these costs, the mining and comminution costs are often significant. For example, typical drilling, blasting, hauling and crushing/grinding costs in a simple flotation or heap leach/solvent extraction/electrowinning operation can reach up to 80% of the total operating costs. A combination of these limitations and difficulties may make conventional processing unviable or uneconomical and it is generally recognised that an alternative approach that could minimise such costs would be extremely advantageous.

To overcome these difficulties and to make projects more economically viable, companies have tended to chase economies of scale and reduce operating costs through efficiencies (i.e., staff reductions and reductions in investment and innovation). However, a paradigm shift away from the concept of bigger being better may be required and an alternative approach could be to adopt a step-change technology that could reduce or eliminate the inherent expensive challenges of conventional processing.

In-situ recovery (ISR, also referred to as in-situ leaching or solution mining) may offer such a step-change approach. ISR refers to the recovery of valuable metals from ore deposits by the circulation of a fluid underground and the recovery of the valuable metal from the fluid at the surface for further processing. It has the potential to be a low-impact and selective mining option, almost the equivalent to keyhole surgery for humans.

References to ISR date back to 177 BC and the Chinese used ISR to recover copper in 907 AD. ISR has been used extensively in the recovery of soluble salts, such as halite (NaCl), trona (Na3(CO3)(HCO3)2H2O), potash (various salts that contain potassium in water-soluble form, such as potassium hydroxide, carbonate, chlorate, chloride, nitrate, sulphate and permanganate), boron and magnesium minerals. The first trials of uranium ISR were initiated in the 1960s in USA and Russia and, by 2013, almost half of the worlds uranium was being mined from ISR operations, including those in Australia, China, Kazakhstan, Russia, USA and Uzbekistan.

A number of experimental, demonstration and commercial copper ISR operations have been undertaken, with the focus being mostly on easily leached oxide material, but to date, no commercial greenfield operations have been established for copper-sulfide deposits. A number of gold deposits, particularly paleochannel deposits, have also been considered for ISR, but, to the best of our knowledge, only limited demonstration and no commercial operations have been established. Generally, ISR has been applied previously only to porous or soft rock deposits and there has been limited uptake to date for hard rock mineral systems.

Many ore bodies will remain unsuitable for an ISR approach due to inherent and local factors (such as geology, hydrology, ore and gangue mineralogy, lack of permeability etc.) and there is no universally applicable ISR process even for those deposits with a favourable predisposition. Characteristics of different deposits vary significantly and factors such as the ore mineralogy, valuable metal location/distribution, target mineral liberation and accessibility, depth and deposit temperature, all affect the requirements and selection of the type of ISR process, which can vary from extraction of metal values from broken ore in pits or stopes (often termed in-place leaching) to designated wellfield design with a solution recovery plant.

The significant economic advantages of ISR compared with other mining methods are that it eliminates or reduces mining costs significantly by avoiding the removal of ore and overburden to surface dumps, stockpiles or operations; avoids comminution costs required prior to beneficiation, flotation or leaching and the associated issues of generation and storage/disposal of tailings. These advantages could allow for currently sub-economic ores to become attractive, for example, by avoiding significant upfront capital and ongoing operating costs. There will, of course, be costs associated with ISR operations. For example, wellfields must be developed, sub-surface access creation may be required and solutions will need to be pumped underground and back to the surface for further processing. However, many of these costs may be incurred incrementally, with the ability to recover metal from pregnant leach solution immediately and recycle lixiviant.

A preliminary estimate of the quantification of the ISR opportunity within Australia for four selected commodities (copper, gold, uranium and nickel) has been made, based on the total sub-economic and inferred resources as classified according to the JORC code. We recognise the limitations of this approach because some currently inferred resources may be classified economic with additional geological evidence and definition. Inferred Australian resources as at December 2013 are substantial (see Table 1) (Britt, 2014) and represent a significant opportunity if it is assumed that ISR could be a potential alternative treatment route for even a small portion of these currently known but not commercial attractive resources. The value of the total Australian sub-economic and inferred resources equates to AUD$B 287 gold, AUD$B 412 copper, AUD$B 358 nickel and AUD$B 34 uranium (based on metal prices of 1647 AUD$/oz Au, 4.07 AUD$/lb Cu, 15023.23 AUD$/t Ni and 24.9 AUD$/lb U).

The trade-off, in economic terms, with a potential ISR approach is the likely or inevitable slower rates of recovery of metal from the target minerals and reduced overall recovery compared with conventional processing. The rate of recovery (e.g., mass of metal per day) is limited by the extent of the well field development, the rate of lixiviant contact with exposed target minerals and any chemistry-related limits, such as maximum lixiviant or solute concentrations. However, in-situ conditions can also provide potentially significant chemistry advantages, for example, if the ore body is at elevated temperature. Mineral reaction rates usually increase with increasing temperature and thus zones with an elevated temperature could be processed more rapidly or with milder, often more selective reagents, than those required to process the ore at surface. These factors can be significant; for example the in-situ temperatures of up to 200C in an ore body that we evaluated recently could result in a very different solution chemistry (solubility and solubility limits, activity, kinetics etc.) from that expected under typical surface processing conditions.

The careful selection of lixiviant to solubilise values could enable the extraction of metals from even deep underground deposits using conventional pumping technology with above-ground processing, and recycling of the lixiviant. This approach is already being used for porous uranium and copper ore bodies, and although access to hard rock may pose some challenges, hard host rock provides some advantages in that lixiviants should be more easily contained, which reduces the environmental risk. The lixiviant system can also be customized for different sections or zones of the ore body depending on such factors as mineralogy and temperature and with advanced real-time production monitoring, lixiviant flow and composition can be tailored to best suit each target ore body zone.

The mining industry tends to leave a legacy of large open pits, waste dumps and tailings dams, which are visually unappealing and pose a latent or active hazard. Besides economic advantages provided by the reduced or complete lack of mining and surface comminution, ISR offers additional advantages in that such an approach could avoid the creation of pits, dumps and tailings dams. Other improved health, safety and environmental outcomes would include the removal of people from underground; a reduction in dust, noise, greenhouse-gas emissions, seismic events and surface footprint; and landslides, deforestation, erosion and siltation, which ensures value extraction without the typical legacy.

ISR processing may also be possible below surface features that cannot be disturbed; such features could be infrastructural or natural, such as protected environmental regions. Remediation of existing mine sites is often essential (e.g.to prevent or contain acid mine drainage), but is expensive, and a number of legacy issues have remained to be dealt with by governments using taxpayers money.

Reduced remediation and rehabilitation requirements, and therefore, reduced mine-closure costs make ISR technology attractive in that much of the restoration of surface aesthetics, as related to conventional processing routes, is not required. In addition, energy, water and the greenhouse gas footprint of many mining projects could have been improved significantly if an ISR approach had been adopted.

Of course, the major environmental challenge of working underground with an ISR approach is the containment of lixiviant and the induced mobility of dissolved metals (particularly where there is potential for sub-surface or groundwater contamination). Many of the permeable, generally oxide ores currently being exploited or considered for ISR lie within or below groundwater systems and many papers have dismissed these opportunities as too environmentally risky. Dry or arid and low-permeability ores may be amenable to the ISR approach, where very different environmental risk profiles would exist. An ISR approach is not without its own environmental challenges and risks but certainly has the potential to avoid others.

ISR provides an opportunity for the creation of new small operations by reducing the barriers to entry, such as the capital costs that are required in traditional operations. A mobile temporary plant, for example, that utilises renewable or intermittent energy sources such as solar power could be established. Such a plant could be used in potentially remote locations and be moved to high-grade or high-recovery zones in the deposit for processing and rapid recovery of value metal to ensure an early positive cash flow and to maximize on the initial return on investment.

This type of approach could enable company conversion from an explorer to an owner/operator with a much smaller capital barrier and provide potential additional opportunities in the METS sector in the design, manufacture and operation of small mobile modular plants. Contract operators could be employed to run the modular plant.

It is even possible that such plants could be leased for processing by different companies in different areas. ISR could also extend mine life and associated jobs and/or increase the target value for existing operations. Closed or closing mines could be revisited for additional value recovery. For example, residual values in pit floors or walls, in low-grade areas adjacent to or between pits, underground and stranded between valuable mineralised zones or small or remote ore bodies may be profitably recovered to process by ISR means.

It may also be possible to progress projects where a political or social risk may not justify a traditional large capital investment. ISR would particularly benefit those deposits that would require cooling before conventional extraction could proceed, as accelerated ISR extraction would exploit the favourable leach kinetics. Besides temperature, pressure may also provide advantages for accelerated leach recoveries and favourably change solution chemistry.

A step change is needed to convert the untapped wealth of currently uneconomic ore bodies into attractive targets for metals recovery and contributors to our economy. ISR may be the minimalist keyhole-mining approach to achieving such an objective. The future mining may involve selective value extraction and no legacy issues about time!

CSIROs hard rock mining research and development merged in 2016 with CRCMining to form Mining3. Mining3 is leading a transformational initiative called InPlace Mining to deliver smaller surface footprints, reduced tailings generation, low environmental impact, higher degrees of automation, and lower capital intensity mines. In-situ mining sits within the range of methodologies that can be deployed, whereby an integrated suite of technologies (some still under development) is essential to the future success of the transformation of mining.

The authors Drs Dave Robinson and Laura Kuhar are leading the Mining3/CSIRO ISR initiative and coordinating myriad projects and welcome participation and feedback.For more information or to find out how to participate in research projects, contact Dr Dave Robinson [email protected]

mineral extraction - an overview | sciencedirect topics

mineral extraction - an overview | sciencedirect topics

Mineral extraction is associated with a diverse range of potentially adverse impacts on environmental and human health. A broad framework to assess potential direct and indirect risks is required, and must incorporate exposure information from geology, geomechanics, toxicology, and epidemiology. To optimize community safety, a major goal is to ensure that all stages of mineral extraction, processing, and use are conducted within a context of careful and transparent health surveillance and environmental monitoring. As with many industries, the balance between risks and benefits of mining must be carefully calibrated. Mining offers a combination of both beneficial and adverse health outcomes for workers and communities. Despite the numerous past ongoing failures to minimize the impacts of mining, it is by no means inevitable that mining in a particular region will lead to profound and long-term human and environmental damage. The approaches and skills offered by the emerging field of medical geology is an important step to avoid penalizing industries and resource-dependent societies, while at the same time optimizing community health.

Mineral extraction (mining) and petroleum and gas production are major resource extraction activities that provide the raw materials to support our economic infrastructure. An enormous amount of pollution is generated from the extraction and use of natural resources. The Environmental Protection Agencys Toxic Releases Inventory report lists mining as the single largest source of toxic waste of all industries in the United States. Mineral extraction sites, which include strip mines, quarries, and underground mines, contribute to surface water and groundwater pollution, erosion, and sedimentation (see Chapter 14). The mining process involves the excavation of large amounts of waste rock in order to remove the desired mineral ore (Fig. 12.6). The ore is then crushed into finely ground tailings for chemical processing and separation to extract the target minerals. After the minerals are processed, the waste rock and mine tailings are stored in large aboveground piles and containment areas (see also Chapter 14). These waste piles, along with the bedrock walls exposed from mining, pose a huge environmental problem because of the metal pollution associated primarily with acid mine drainage. Acid mine drainage is caused when water draining through surface mines, deep mines, and waste piles comes in contact with exposed rocks containing pyrite, an iron sulfide, causing a chemical reaction. The resulting water is high in sulfuric acid and contains elevated levels of dissolved iron. This acid runoff also dissolves heavy metals such as lead, copper, and mercury, resulting in surface and groundwater contamination. Wind erosion of mine tailings is also a significant problem.

Petroleum and natural gas extraction pose environmental threats such as leaks and spills that occur during drilling and extraction from wells, and air pollution as natural gas is burned off at oil wells (Chapter 14). The petroleum and natural gas extraction process generates production wastes including drilling cuttings and muds, produced water, and drilling fluids. Drilling fluids, which contain many different components, can be oil based, consisting of crude oil or other mixtures of organic substances like diesel oil and paraffin oils, or water based, consisting of freshwater or seawater mixed with bentonite and barite. Each component of a drilling fluid has a different chemical function. For example, barite is used to regulate hydrostatic pressure in drilling wells. As a result of being exposed to these drilling fluids, drilling cuttings and muds contain hundreds of different substances. This waste is usually stored in waste pits, and if the pits are unlined, the toxic chemicals in the spent waste cuttings and muds, such as hydrocarbon-based lubricating fluids, can pollute soil, surface, and groundwater systems. Produced water is the wastewater created when water is injected into oil and gas reservoirs to force the oil to the surface, mixing with formation water (the layer of water naturally residing under the hydrocarbons). At the surface, produced water is treated to remove as much oil as possible before it is reinjected, and eventually when the oil field is depleted, the well fills with the produced water. Even after treatment, produced water can still contain oil, low-molecular-weight hydrocarbons, inorganic salts, and chemicals used to increase hydrocarbon extraction.

Mined and extracted resources can also be potential pollutants once they are used for production. For example, fossil fuels are key resources for energy production. Coal-burning power plants produce nitrogen and sulfur oxides, which are known to be the primary causes of acid rain (see Chapter 17). In addition, fossil fuel combustion produces carbon dioxide, which is a primary culprit in global climate change.

The environmental impacts of mineral extraction varies according to the type of mineral and the extent of its deposit, with the significance of the impact changing throughout the working life of a mine or quarry. Often, negative impacts related to its exploitation continue long after the deposits have been worked and are no longer economically viable. It is estimated that a mean of 0.3% of the land surface has been affected by mining, amounting to some ~400,000km2 (Hooke and Martn-Duque, 2012). Naturally with this scale of operations, impacts can be severe. Typical issues are aspects of mine operation themselves (Fig. 3), the impact of mining subsidence, the release of toxic materials during and after mining, dealing with mine wastes, and post-exploitation quarry or mine restoration.

There is a broad range of issues associated with mining. Quarries produce blast noise and vibration, which can lead to increased rock-fall and groundwater pollution. Dust introduced into the atmosphere can be troubling to adjacent communities, especially where particulate matter contains potentially harmful metals. Smelting emissions from metal mines also increase the potential for acid rain and windblown distribution of toxic metals. Restoration and stabilization of wastes are essential, but these can be difficult for a variety of reasons, particularly when vegetation that could be useful in binding surfaces is inhibited by the toxicity of the waste material itself.

The release into the local environment of potentially toxic substances is a particular problem. For example, acid mine drainageassociated with the oxidation of iron sulfides in minescan be problematic, especially where the mine operations have concluded (Gray, 1997). This is particularly the case as the mining cavities fill with water and produce problematic outflow, including iron-rich (ochre) waters from abandoned coal and base metal mines (Fig. 4). The resulting acidity of the water can lead to elevated concentrations of Co, Mn, Ni, Pb and Znsome of which are readily soluble and, therefore, available for absorption by aquatic organisms (e.g. Krishna and Govil, 2004). Additionally, the widespread use of cyanide or mercury to release gold in some mining operations, if not properly managed, has caused environmental problems.

Other waste materials are a growing issue, particularly where there is opencast extraction. About 50 million tons/year of waste rock from coal-mining are generated in the limited area of the thickly populated Upper Silesian Coal Basin in Poland resulting in 380 coal-mining waste dumps (Szczepanska and Twardowska, 1999). Although much waste rock is being reused for civil engineering purposes in the same area, not all can be utilized in this way.

Quarry and mine restoration is also an important environmental remediation task. For mines, it is important, first of all, to ensure the safety of the underground workings themselves and then to monitor such issues as the build-up of gases and acid mine drainage. In other cases, the mine workings may present a hazard in the form of future subsidence. Pit-head machinery and processing works, which may have used chemical processing, are also be a concern that requires specialist attention. Finally, the mine wastes themselves, whether in ponds or dumps, must be dealt with. For quarries, restoration demands reflect the nature of the materials quarried. For example, production-blasted quarry faces in crystalline rock can be unsafe and their instability must be mitigated. Restoration depends very much on the projected end use of the quarry; if left as a void, then faces will require engineering attention. This is particularly so given that many quarries are now being used for brownfield development. In other cases, the void will be backfilled with inert material, or landfillthough pressure is on to reduce this approach.

Are any areas within the AA currently undergoing mining, quarrying or extraction of any form (other than peat mining)?a.No indication of mining, quarrying or extractionb.Historical areas of mining, quarrying or extraction, currently inactivec.Currently active areas of mining, quarrying or extraction.d.Unknown

Are any areas within the CA currently undergoing mining, quarrying or extraction of any form (other than peat mining)?a.No indication of mining, quarrying or extractionb.Historical areas of mining, quarrying or extraction, currently inactivec.Currently active areas of mining, quarrying or extraction.d.Unknown

There are other less common processes for mineral extraction from brines. One of these reported methods for salt extraction is the removal of inorganic compounds via supercritical water [33]. Supercritical water appears when water is over its critical pressure and temperature, which produces a behavior between gases and liquids. This technology includes different stages of precipitation and separation with energy recovery and temperature recovery.

Chemical precipitation of salts was also proposed by Jibril and Ibrahim [34] for the extraction of chemicals from brines by means of processes involving chemical reaction to convert NaCl into Na2CO3, NaHCO3, and NH4Cl or techniques such as the eutectic freeze crystallization as a novel technique for salt separation from water streams [35].

Although it was not exactly designed as a method for mineral production, the SPARRO process (slurry precipitation and recycling RO) forces the controlled precipitation of soluble salts with seeded crystals and then it could be combined with any of the above-mentioned technologies.

Other technologies for salt removal or production are combined or hybrid processes including RO, NF, and precipitation. Almarsi et al. [36] obtained Ca6Al2(SO4)3(OH)12 and CaSO4 from brine in a two-stage RO with an intermediate NF with precipitation, and Telzhensky et al. [37] also proposed NF to separate magnesium ions for post RO stabilization. Alternatively, concentrate from NF could be used for struvite precipitation from wastewater.

A forest established on sites reclaimed after mineral extraction is usually more susceptible to destructive agents such as drought, insect attack, or infertility than that on undisturbed land. It is therefore vital that attention be paid to the performance of the forest as it develops, especially in its early years. Regular site visits are necessary to check protective measures and the efficacy of operations such as weed control. Tree failure should be investigated and remedies put in place in case of significant loss. In addition, monitoring of water quality may be necessary for those sites where there is a risk of degradation of water quality, and consequent pollution to surface or groundwaters supplied from the site.

Because of its reliance on shipping and mineral extraction industries, economic growth in New Orleans was historically slow, a structural constraint caused by a lack of social development. The few industries in New Orleans, such as oil and tourism, periodically declined during oil busts and national economic downturns (Freudenburg et al., 2009). The economy of New Orleans has never been well diversified (Marks, 2010a, 2010b).

The severe disruption in the tourism, seafood, and oil industry after Katrina was a significant threat to livelihoods in New Orleans. For example, the disaster lead to disruption of tourism, and an exacerbation of income stability for both performers and teachers of music. People in New Orleans, however, had some access to alternate livelihoods after Katrina (Downey, 2016). Mentoring for musicians helped in the formation of new opportunities in music, through traditional brass bands, performances at restaurants and clubs, and performances during tours (Morris & Kadetz, This Volume, Chap. 10).

Mining industries need process improvements across all facets including mineral extraction, processing, transportation, and marketing to remain cost efficient and gain a firm foothold in the competitive market. Application of business process management (BPM) helps analyze and optimize mining organization's processes, promotes better collaboration as well as coordination among various departments to improve efficiencies and ensure best results (www.actgov.org/knowledgebank/whitepapers/Documents/Sponsor%20White%20Papers/IBMCloud.pdf). BPM can automate field reporting systems to improve operations and maintenance by up-to-date operational information. Cloud computing can provide a relatively inexpensive solution to ensure relevant and accurate information to sales and marketing personnel on production schedules, output and inventory across a wide variety of product specifications.

Mining companies can extract benefits in at least four areas by use of BPM technology. It can help improve operations and maintenance by providing managers with up-to-date operational information. It can establish better collaboration and coordination between production and sales. Mining companies are highly dependent on the reliability of the equipment and vehicles used for mining and transportation of their products. Cloud computing can play a key role in determining how successful a company's operation and management efforts are in maximizing the uptime of machinery and vehicles used in mining, handling, and storage. It can be used to automate the recordkeeping for each vehicle and piece of equipment, keep track of warranties, and maintain planned schedules. Breakdowns and unplanned repairs can be monitored and best practices can be established for operating each unit. BPM can be used to set up a cost-effective repository quickly and efficiently for operating manuals and engineering drawings. This would allow access for employees from any department in the company as well as outside parties who have been given permission.

There are now several firms that offer BPM software products. Each product has its own unique features and user interface, but what they have in common is the ability to automate almost any business process regardless of industry or functional area.

Geometallurgy is regarded as a new science in the area of economic mineral extraction. It is difficult to know when exactly geometallurgy emerged and when the term was first framed, but certainly it appears to have evolved in the late 1980s or early 1990s. However, real emergence of the study of geometallurgy dates mostly from 2000 and on (Hoal, 2008; Williams, 2013). There are various, but essentially the same, definitions for geometallurgy, as follows:

Geometallurgical mapping is a team-based approach that documents variability within an orebody and quantifies the impact of geology (host rocks, alteration, and structure) and mineralogy on grinding, metallurgical response, and metal recovery processes. It is an important tool to reduce the technical risk associated with new mine developments or expansions (Williams and Richardson, 2004).

The geologically informed selection of a number of test samples to determine metallurgical parameters and the distribution of these parameters through an orebody using an accepted geostatistical technique to support metallurgical process modeling (SGS, 2013).

An interdisciplinary approach that links the geological, geochemical, and mineralogical characteristics to the metallurgical performance of an orebody. It is a framework and methodology for process design, mine planning, and plant optimization (Zhou, 2013).

extraction and processing of minerals & the environmental impacts of mineral use - video & lesson transcript

extraction and processing of minerals & the environmental impacts of mineral use - video & lesson transcript

Elizabeth, a Licensed Massage Therapist, has a Master's in Zoology from North Carolina State, one in GIS from Florida State University, and a Bachelor's in Biology from Eastern Michigan University. She has taught college level Physical Science and Biology.

In a previous lesson, we learned about minerals, which are inorganic compounds, such as ores (like copper) and precious stones (like diamonds). The word mining sounds a lot like mineral, and that's no accident because mining is how minerals are removed from the ground. There are several different ways minerals can be extracted from the earth, but the two main methods are called surface mining and subsurface mining.

Surface mining is just what it sounds like - removing minerals that are near the earth's surface because this is where the ore deposits are located. When the ore deposits are very large, open-pit mining is utilized. A large, open pit is created as machines scrape off any earth that is not ore and set it to the side. This material is called overburden, and as the overburden is scraped off, it's piled into spoil banks.

After the overburden is cleared from the ore, explosives are used to break up the ore material that is being removed from the ground, which is then taken away to be refined. The size of the ore bed increases as mining continues, and eventually, the pit becomes a very large bowl-shaped hole in the earth's surface. When the ore is found in a wide area but it's not very deep in the ground, strip mining is used.

In strip mining, instead of creating one large pit in the ground, long narrow strips are dug out. The overburden is removed and piled up along the strip. Once the ore is removed, the overburden is dumped back into the strip. While this may sound like a good method because the holes are re-filled instead of left open, the land actually looks more like a washboard after strip mining because of all of the re-piled soil.

Some minerals are found very deep below Earth's surface - sometimes hundreds or thousands of feet deep! To remove these minerals from the ground, subsurface mining is used. In subsurface mining, a long tunnel is created either horizontally or vertically. The tunnel walls are reinforced with wood and ventilation shafts are created to provide air to the miners underground. The minerals themselves are removed a number of different ways.

One way is to blast apart the material and then send the ore pieces up to the surface in carts. Another method is longwall mining, which is when coal is sheared from the wall and collected on a conveyor belt, much like a potato peeler shears away layers of a potato. This is a very efficient way of extracting coal from an underground mine. Another method is solution mining, which is when hot water is injected into the ore to dissolve it. Once the ore is dissolved, air is pumped into it, and it's bubbled up to the surface.

While mining provides us with the minerals we need, it is also very destructive because it disrupts the landscape both on the surface and underground. It also causes quite a bit of pollution and can harm or kill mine workers. Surface mining is destructive to landscapes because it can cause changes in the topography and drainage and strips the land of vegetation, soil and rocks. The spoil banks of surface mining erode and weather away, and rainfall leaches toxic chemicals into the earth. In some cases, entire mountaintops have been removed for surface mining!

Subsurface mining is actually less disruptive to the earth and produces less waste than surface mining, but it's also much less effective and more dangerous. Many workers die in mine collapses, which then also leaves behind a large hole from caving in of the ground above. Water may leak into the mine and dissolve toxic chemicals that may leak into aquifers and drinking water supplies. Explosions in old mining tunnels may also occur because the natural gas underground ignites very easily.

Besides erosion problems and changes to the landscape, mining also causes pollution in the air and water. Abandoned coal mines lead to acid mine drainage, which is water that is full of metals and toxins. Much like hot water dripping through coffee in a filter, rainwater picks up the harmful components in the ground and carries them off as surface and groundwater runoff. This runoff can end up in streams, rivers and lakes that are nearby.

Smelting is the process of heating ores to release the metals in them. This process separates the impurities from the metal, but also creates air pollution because gases that are created as by-products (such as sulfur dioxide) may escape and reach the air.

Mining is the removal of minerals from the ground. Once removed, minerals are then processed and refined for our everyday use. We use minerals for a variety of things, such as household products, jewelry and energy for cars and buildings. Surface mining removes ore deposits that are close to the surface, and subsurface mining removes minerals that are deep underground.

While mineral use is very important to us, there are also many environmental impacts, such as erosion, air and water pollution, land destruction and harm to mine workers. With new technologies and a conscious effort to reduce the negative effects of mining, we may be able to find a balance in how we use these important resources and reduce our impacts on the earth.

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