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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.
This was hand-excavated to 201 m (660 ft) by 1911, and the hand-dug pit was sightly larger than the Big Hole. The Palabora Open Pit – mechanically excavated by Palabora Mining Company, in Phalaborwa, Limpopo Province. The pit is 898m deep and 1846m across on top. [5] Voorspoed diamond mine
Full-scale mining using steam shovels was started in 1917, making the New Cornelia the first large open pit mine in Arizona. [6] Mining and treatment of the underlying but lower-grade copper sulfide orebody began in 1924. New Cornelia came under the ownership of Phelps Dodge in 1931 when Calumet and Arizona merged with Phelps Dodge.
The mine was started as the Chino Copper Company in 1909 by mining engineer John M. Sully and Spencer Penrose, [1] [2] [3] and is currently owned and operated by Freeport-McMoRan Inc. subsidiaries. The area where the mine is located is at an average elevation of 5,699 feet (1,737 m).
The Montana Cyanide Process Open Pit Mining Prohibition Initiative, also known as I-137, was a successful initiative on the November 3, 1998 ballot in Montana. It sought to prohibit "new open-pit gold and silver mines that used heap and vat cyanide leach processing ".
Mining of sulfide minerals began in the district in 1864. Placer deposits were mined out by 1867. Silver vein lodes were then the most productive until copper was discovered in 1881. Open-pit mining started in 1955. Copper has historically been the main metal produced, though lead, zinc, manganese, silver and gold have been produced at various ...
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