Open-pit mining , also known as open-cast or open-cut mining and in larger contexts mega-mining , is a surface mining technique that extracts rock or minerals from the earth.
48-461: Mount Keith Mine is an open pit nickel mine in Western Australia . It is operated by BHP . The site's closest landmark is the town of Wiluna , 85 km (53 mi) to the north. The mine, originally opened in 1995, is operated by BHP and part of its Nickel West operations. Having originally been built by WMC Resources , it changed ownership in 2005 when BHP acquired WMC. The mine
96-447: A mine that contribute to this load: drilling , blasting, loading, and hauling . Waste rock is hauled to a waste dump. Waste dumps can be piled at the surface of the active pit, or in previously mined pits. Leftover waste from processing the ore is called tailings , and is generally in the form of a slurry . This is pumped to a tailings dam or settling pond, where the water is reused or evaporated. Tailings dams can be toxic due to
144-524: A number of fatalities throughout its operation, most notably on 27 April 1977, when five employees were killed in one incident. The nickel deposit at Leinster was discovered in 1971 by Western Selcast Pty Ltd. To develop this asset, the Agnew Mining Company was formed in 1974, of which 60 percent were owned by Western Selcast and 40 percent by MIM Holdings , and development of the mine started in 1976, with underground mining commencing in 1978 in what
192-429: A number of worked-out mines. After mining ends at a location, the mine area may undergo land rehabilitation . Waste dumps are contoured to flatten them out, to further stabilize them. If the ore contains sulfides it is usually covered with a layer of clay to prevent ingress of rain and oxygen from the air, which can oxidize the sulfides to produce sulfuric acid , a phenomenon known as acid mine drainage . This
240-701: A potential restart. The decision was estimated to affect 1,600 workers and the mines and smelters but BHP committed to offer all employees affected a redeployment or redundancy. Mount Keith is part of BHP's Nickel West operations, which includes, apart from Mount Keith, the Leinster Nickel Mine , the Kambalda Nickel Concentrator , the Kalgoorlie Nickel Smelter and the Kwinana Nickel Refinery . After crushing and processing
288-477: A result of room and pillar mining . Untopping removes the overburden from above this, opens up the mine from above, and then allows the previously 'trapped' minerals to be won. Untopping was a feature of Welsh slate workings in the 1930s and 2000s, where Martyn Williams-Ellis, manager at Llechwedd found that earlier Victorian workings could be kept profitable with the newly mechanised techniques for bulk excavation to extract their pillars, and more recently across
336-562: A substantial interest in ACM, owning 20 percent of the company's shares in 1987, but soon sold these again for a profit. In May 1991, ACM's managing director approached WMC as well as a few other mining companies with the request of taking over the former. WMC Resources concluded that it wasn't interested in the takeover but wanted to acquire the Mount Keith project. Among the companies approached, Normandy Posiedon , led by Robert Champion de Crespigny ,
384-450: Is a crucial aspect of determining whether or not a geotechnical engineering design for open-pit slopes is attainable. Groundwater control systems, which include dewatering and depressurization wells, may also have a large impact on local groundwater. Because of this, an optimization-based version of the control system is required to ensure that local and regional hydro-geological impacts are within acceptable ranges. Open Pit depressurization
432-474: Is also sourced from the Cliffs mine, which opened in 2008 and is located south of the Mount Keith mine, supplying ore to both. During the development of the mine, on 27 April 1977, five employees died at the mine's Perseverance shaft after falling 35 metres in an ore bucket. In 1981, an employee was killed in an underground cave-in. On 11 December 1985, two men died of asphyxiation in the underground operation of
480-509: Is determined by the size of the equipment being used, generally 20–40 metres wide. Downward ramps are created to allow mining on a new level to begin. This new level will become progressively wider to form the new pit bottom. Most walls of the pit are generally mined on an angle less than vertical. Waste rock is stripped when the pit becomes deeper, therefore this angle is a safety precaution to prevent and minimize damage and danger from rock falls. However, this depends on how weathered and eroded
528-515: Is located on the north end of the 800 km (500 mi) long Norseman - Wiluna Greenstone belt , with nickel sulfide deposits of the dyke -like or sill deposit type. The important known nickel deposits are in the ultramafic rocks of the lower cycle, around 2700 Ma old. In 1971, the mine was thought to be able to provide 10% of the world's demand for nickel; in 1992 it was estimated as containing 270 million tons of sulfide ore, grading 0.6% nickel, enough for about twenty years. The deposits
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#1732898842249576-457: Is scheduled to be reviewed in February 2027 but BHP would continue to spend $ 450 million annually on its nickel operations to facilitate a potential restart. The decision was estimated to affect 1,600 workers and the mines and smelters but BHP committed to offer all employees affected a redeployment or redundancy. Leinster is part of BHP's Nickel West operations, which includes, apart from Leinster,
624-401: Is the process of removing tensions or pressure from different areas of a mine. Depressurization helps to make open-pit mines more stable and secure. By using an integrated mine slope depressurization program the likelihood that mine plans can be achieved, and at an acceptable level of risk increase drastically. Depressurization allows considerable expansions of a mine, and can extend the life of
672-559: 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
720-557: Is then once more transported by rail, now to the Kwinana Nickel Refinery. At Kwinana, it is converted to nickel metal at a grade of 99.8 percent. This product is then shipped via the Port of Fremantle . Production figures published by the company for the whole Nickel West Operations and not broken down to individual mines. In 2020–21, Nickel West produced 89,000 tonnes of nickel, an eleven percent increase of production in comparison to
768-634: The Lusatian Lake District , the Central German Lake District or the Upper Palatinate Lake District. A particular concern in the formation of these lakes is acid mine drainage . Open-pit mines create a significant amount of waste. Almost one million tons of ore and waste rock can move from the largest mines per day, and a couple thousand tons moved from small mines per day. There are generally four main operations in
816-632: The Mount Keith Mine , the Kambalda Nickel Concentrator , the Kalgoorlie Nickel Smelter and the Kwinana Nickel Refinery . BHP, through its Nickel West operations, mines Nickel sulphide in open-cut and underground operations northern part of the Goldfields region of Western Australia. Nickel concentrate is then dried and transported by rail to the Kalgoorlie Nickel Smelter. The resulting product, containing approximately 68 percent nickel,
864-574: The Philippines and Indonesia . In 2024, nickel mining and processing was one of the main causes of deforestation in Indonesia . Open-pit cobalt mining has led to deforestation and habitat destruction in the Democratic Republic of Congo . Open-pit mines operating in an area with heavy groundwater features may eventually face hydrology-related problems. This includes heaving and bursting of
912-418: The mineral resource is exhausted, or an increasing ratio of overburden to ore makes further mining uneconomic. After open-pit mines are closed, they are sometimes converted to landfills for disposal of solid waste. Some form of water control is usually required to keep the mine pit from becoming a lake. Several former open-pit mines have been deliberately converted into artificial lakes, forming areas such as
960-399: The 1980s, the move towards fly in-fly-out operations rather than the workforce residing in fully developed towns reduced the potential cost of the project and ACM started to review the project again in 1988. ACM entered an equal joint venture with Outokumpu to develop Mount Keith at a projected cost of A$ 417.4 million and a start-up date of May 1992. WMC Resources , WMC, for a time, held
1008-466: The Finnish company. WMC declared that it was ready to proceed with the project on 11 February 1993, now at an estimated cost of A$ 450 million, but Outokumpu was unwilling to commit to the mine and, 11 days later, sold its stake back to WMC for cash and considerations. Construction of the mine commeced soon after and activities at the mine peaked in 1994 with a construction work force of 1,000 people on site at
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#17328988422491056-402: The areas surrounding open-pit mines. Open-pit gold mining is one of the highest potential mining threats on the environment as it affects the air and water chemistry. The exposed dust may be toxic or radioactive, making it a health concern for the workers and the surrounding communities. Open-pit nickel mining has led to environmental degradation and pollution in developing countries such as
1104-472: The environment. The dumps are usually fenced off to prevent livestock denuding them of vegetation. The open pit is then surrounded with a fence , to prevent access, and it generally eventually fills up with ground water . In arid areas it may not fill due to deep groundwater levels. In Germany, the world's largest producer of lignite (virtually all of which these days is mined open-pit), the former mines are usually converted to artificial lakes . To mitigate
1152-429: The hole. The interval of the benches depends on the deposit being mined, the mineral being mined, and the size of the machinery that is being used. Generally, large mine benches are 12 to 15 metres thick. In contrast, many quarries do not use benches, as they are usually shallow. Mining can be conducted on more than one bench at a time, and access to different benches is done with a system of ramps. The width of each bench
1200-454: The mine by 10 to 15 years. One technique used in depressurization is annealing. Annealing is the slow heating and cooling of a metal, alloy or glass. This slow heating and cooling relieves the internal stress of surrounding areas. Annealing will increase a material's workability and durability, which overall increases open-pit mine safety. When groundwater pressures cause problems in open-pit mines, horizontal drains are used to aid in accelerating
1248-528: The mine employed 950 people. In 2009, BHP reduced the mine's activity, laying off 300 employees. Due to an oversupply of nickel and a consequent drop in nickel prices, BHP announced on 11 July 2024 that it would temporarily close all of its Nickel West operations in October 2024 and place them in care and maintenance . This decision is scheduled to be reviewed in February 2027 but BHP would continue to spend $ 450 million annually on its nickel operations to facilitate
1296-450: The mine floor due to excessive uplift pressure. A groundwater control system must be installed to fix problems caused by hydrology. The formation of an appropriate open-pit slope design, changes throughout the life of a mine. It is based mainly on an ever-increasing understanding of the rock mass conditions, including groundwater and associated pressures that may be acting within the slopes. The reduction of groundwater related to pore pressures
1344-584: The mine to Leinster Nickel Operations while it renamed its local gold mine, the Emu mine, to Leinster Gold Operations, now the Agnew Gold Mine . WMC upgraded the concentrator to a capacity of one million tonnes within its first year of operations, to be doubled in the following two years. At the time of the closure in 1986, the nickel price had fallen to U$ 1.70 per pound while, on reopening it in 1989, prices had recovered to U$ 8.30 per pound. In 2005, WMC Resources
1392-490: The mine was subsequently enlarged to 500,000 tonnes in 1980 and 750,000 tonnes in 1984. In 1985, BP acquired the parent company of Western Selcast, Selection Trust , and therefore a 60 percent interest in the mine. On 15 August 1986, operations at the Agnew Mine ceased because of declining nickel prices, with the mine being placed in care and maintenance. The closure of the mine affected WMC Resources negatively as it reduced
1440-422: The most dangerous sectors in the industrial world . It causes significant effects to miners' health, as well as damage to the ecological land and water. Open-pit mining causes changes to vegetation, soil, and bedrock, which ultimately contributes to changes in surface hydrology, groundwater levels, and flow paths. Additionally, open-pit produces harmful pollutants depending on the type of mineral being mined, and
1488-410: The ore on site, nickel concentrate is transported by road from the mine to Leinster for drying and subsequent on-shipping. Production figures published by the company for the whole Nickel West Operations and not broken down to individual mines. In 2020–21, Nickel West produced 89,000 tonnes of nickel, an eleven percent increase of production in comparison to the previous year. The average sale price for
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1536-446: The presence of unextracted sulfide minerals , some forms of toxic minerals in the gangue , and often cyanide which is used to treat gold ore via the cyanide leach process . If proper environmental protections are not in place, this toxicity can harm the surrounding environment. Open-pit mining involves the process of disrupting the ground, which leads to the creation of air pollutants. The main source of air pollutants comes from
1584-557: The previous year. The average sale price for the produced nickel was US$ 16,250 per tonne. In 2021–22, Nickel West's nickel production fell to 77,000 tonnes. As of 2022, mining occurs at the Camelot open-pit and the Venus and B11 underground operations, while mining at the Rocky’s Reward open pit ceased in 2021. Underground mining at Leinster was suspended between 2013 and 2016. Ore for the mine
1632-407: The problem of acid mine drainage mentioned above, flooding is often done with the water of nearby rivers instead of using groundwater alone. In some cases, calcium oxide or other basic chemicals have to be added to the water to neutralize the pH -value. Gold is generally extracted in open-pit mines at 1 to 5 ppm (parts per million) but in certain cases, 0.75 ppm gold is economical. This
1680-401: The produced nickel was US$ 16,250 per tonne. In 2021–22, Nickel West's nickel production fell to 77,000 tonnes. Open-pit mining Open-pit mines are used when deposits of commercially useful ore or rocks are found near the surface where the overburden is relatively thin. In contrast, deeper mineral deposits can be reached using underground mining. Open-pit mining is considered one of
1728-404: The rocks are, and the type of rocks involved. It also depends on the amount of structural weaknesses occur within the rocks, such as a faults , shears , joints or foliations . 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
1776-412: The slope depressurization process. Which helps to prevent large scale slope failure in the mine. Horizontal drains are used to lower pore pressure by reducing groundwater head, which enhances slope stability. A form of open-cast quarrying may be carried out as 'untopping'. This is done where a previous underground mine is becoming uneconomic or worked-out, but still leaves valuable rock in place, often as
1824-542: The throughput in its Kalgoorlie smelter. With BP Australia and MIM Holdings willing to sell the mine and WMC being able through its other state assets to take a long-term approach to nickel mining in Western Australia, the mine was sold in late 1988, with BP's interest sold for an undisclosed amount while MIM Holdings sold theirs for A$ 120 million. WMC subsequently reopened the mine, resuming operations in May 1989. WMC renamed
1872-515: The time. Commissioning of the plant began in November 1994 and shipment of first ore took place in 1995. In 2005, WMC Resources was acquired by BHP , which bundled WMC's nickel assets under its Nickel West brand, which became the largest nickel producer in the state, producing a combined 67,000 tonnes out of the 180,000 tonnes produced in Western Australia in 2004–05. At the time of the WMC acquisition by BHP,
1920-416: The transportation of minerals, but there are various other factors including drilling, blasting and the loading and unloading of overburden. These type of pollutants cause significant damage to public health and safety in addition to damaging the air quality. The inhalation of these pollutants can cause issues to the lungs and ultimately increase mortality. Furthermore, the pollutants affect flora and fauna in
1968-480: The type of mining process being used. Miners typically drill a series of test holes to locate an underground ore body. From the extracted samples, they can determine the extent of the ore. This helps them determine the likely location of the veins or benches of ore and its commercial value. Open-pit mines that produce building materials and dimension stone are commonly referred to as quarries . Open-cast mines are dug on benches , which describe vertical levels of
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2016-466: 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. A haul road is usually situated at the side of the pit, forming a ramp up which trucks can drive, carrying ore and waste rock. Open-pit mines are typically worked until either
2064-443: The world. Listed are the world's ten largest open-pit mines in 2015. Leinster Nickel Mine Leinster Nickel Mine is a surface and underground nickel mine , 5 km north of Leinster, Western Australia . The deposit was discovered in 1971 and the mine opened in 1978, operated by the Agnew Mining Company. It was purchased by WMC Resources in 1988 which, in turn, was taken over by BHP in 2005. The mine has suffered
2112-515: 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 can be extracted at grades as low as 0.11% to 0.2%. Open-pit mining is a common method to extract minerals and samples from the Earth. Due to being cost-effective, this method is very popular and is used all over
2160-565: Was acquired by BHP , which bundled WMC's nickel assets under its Nickel West brand, which became the largest nickel producer in the state, producing a combined 67,000 tonnes out of the 180,000 tonnes produced in Western Australia in 2004–05. At the time of the WMC acquisition by BHP, the mine employed over 1,100 people. Due to an oversupply of nickel and a consequent drop in nickel prices, BHP announced on 11 July 2024 that it would temporarily close all of its Nickel West operations in October 2024 and place them in care and maintenance . This decision
2208-460: Was interested in ACM's gold projects, and WMC and Normandy agreed to make a joint bid for the company and to split the assets afterwards, with WMC receiving the nickel assets and Normandy the gold ones. The joint offer was eventually successful, with the final transactions completed in June 1992. The final deal saw Outokumpu re-involved in the project, with WMC selling 50 percent of the Mount Keith project to
2256-444: Was originally discovered through exploration drilling by Metals Exploration Limited in 1969. Australian Consolidated Minerals, ACM, initially held a 16 percent stake in the venture, something the company gradually increased to 100 percent by 1988. Despite the early discovery, the mine was not developed at the time because of low nickel prices in the 1970s and the project's large infrastructure costs. Changes to Western Australian mining in
2304-505: Was then referred to as the Agnew Mine . In May 1978, a conventional concentrator with an annual capacity of 350,000 tonnes was commissioned at the mine, with the concentrate processed at WMC Resources 's Kalgoorlie Nickel Smelter. The concentrate was transported by road to Leonora , and from there by rail to Kalgoorlie . The mine was officially opened on 5 November 1978 by Charles Court , Premier of Western Australia . The concentrator of
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