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Open-pit mining, also known as open-cast or open-cut mining and in larger contexts mega-mining, [1] is a surface mining technique that extracts rock or minerals from the earth. 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 ...
Gold miners excavate an eroded bluff with jets of water at a placer mine in Dutch Flat, California sometime between 1857 and 1870.. The modern form of hydraulic mining, using jets of water directed under very high pressure through hoses and nozzles at gold-bearing upland paleogravels, was first used by Edward Matteson near Nevada City, California in 1853 during the California Gold Rush. [3]
[5] [6] Mining at the site by shafts began in the 1920s. Pacific Coast Borax later became U.S. Borax, which subsequently opened the current open-pit mine in 1957. U.S. Borax was later acquired by Rio Tinto Group, which continues to operate the mine. A pilot project to produce lithium by sifting through mining waste began in 2019. [7]
Open-pit mining accounts for 60% of the country's mining production value and is critical for extracting key resources like gold, silver, copper and strategic minerals like lithium.
The Mountain Pass Rare Earth Mine and Processing Facility, owned by MP Materials, is an open-pit mine of rare-earth elements on the south flank of the Clark Mountain Range in California, 53 miles (85 km) southwest of Las Vegas, Nevada. In 2020 the mine supplied 15.8% of the world's rare-earth production.
This may be done by open-pit mining or by various surface excavating equipment or tunneling equipment. Placer mining is frequently used for precious metal deposits (particularly gold) and gemstones, both of which are often found in alluvial deposits—deposits of sand and gravel in modern or ancient stream beds, or occasionally glacial deposits ...
The Mexican Mining Chamber (Camimex) opposes the ban on open-pit mining, saying such a prohibition would cause a 1% contraction in the country's GDP and threaten some 200,000 jobs.
Once a mine closes, mining facilities that occupy a small area of the disturbed land can either be salvaged or town down. [13] The main visual and aesthetic impacts of mining are the open pits and waste rock disposal areas. Open-pit mining disturbs larger areas than underground mining making the visual impacts much greater. [13]