|
Gold mining in Nevada, a state of the United States, is a major industry, and one of the largest sources of gold in the world. Nevada currently mines 79% of all the gold in the United States, which is equivalent to in 2009.〔"Nevada slips in global gold output," ''Mining Engineering'', October 2010, p.13.〕 Total gold production from Nevada recorded from 1835 to 2008 totals , worth over US $228 billion at 2011 prices.〔(Update on Production and Exploration Activity in Nevada - 2009 ) at Nevada Bureau of Mines and Geology〕 Almost all the gold in Nevada comes from large open pit mining and cyanide heap leaching recovery. A number of major mining companies, such as Newmont Mining, Goldcorp and Barrick Gold Corporation, operate gold mines in the state. Active gold mines include those at Jerritt Canyon and Carlin. Unlike coal and oil extraction, where mining companies pay royalties for minerals obtained from public lands, gold mining companies do not pay any royalties for deposits claimed on federal public lands. This is because gold mines on public land operate under the General Mining Act of 1872.〔NBC News, Fleecing of America, March 15, 2010, http://www.msnbc.msn.com/id/3032619/#35883250〕 Although Nevada was known much more for silver in the 19th century, many of the early silver-mining districts also produced considerable quantities of gold. The Comstock Lode, for instance, produced of gold through 1959, and the Eureka district produced . And the Robinson copper mine has produced well over gold, along with over 4 billion pounds (1,500,000 tonnes) of copper. ==Carlin Trend== Gold was discovered in the vicinity of Carlin in Eureka County in the 1870s, but production was small. Placer deposits were discovered in 1907, but the deposits were too small to cause much excitement. It was not until 1961 that the Newmont Mining Corporation found the large low-grade gold deposit at Carlin that the mining industry began to take notice. The Carlin mine began producing gold in 1965, but at the price then of $35 per troy ounce, the ore grade was still too low to cause a rush to northern Nevada. It was not until the gold price shot up in the late 1970s that mining companies rushed to look for similar deposits.〔Donald M. Hausen and Paul F. Kerr (1969) ''Fine gold Occurrence at Carlin, Nevada'', in ''Ore Deposits of the United States, 1933-1968'', New York: American Institute of Mining Engineers, p.908-940.〕 The Carlin Trend, part of what is also known as the Carlin Unconformity by geologists, is wide and long running northwest-southeast, has since produced more gold than any other mining district in the United States. The trend surpassed of gold in 2002. The Carlin and other mines along the trend pioneered the method of open-pit mining with cyanide heap leach recovery that is today used at large low-grade gold mines worldwide. New ore deposits are still being opened along the trend. The South Arturo deposit was discovered by Barrick Gold in 2005. The deposit contains an estimated of gold.〔Ed Cope and others, "South Arturo: a recent gold discovery on the Carlin Trend," ''Mining Engineering'', Jan. 2008, p.19-25.〕 Gold Standard Ventures is currently exploring the Railroad project on the southern portion of the Carlin Trend, within the historic Bullion Mining District and has drill intercepted Carlin styled gold mineralization in 2011/2012. Active gold mines also include Jerritt Canyon and the Getchell Mine. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gold mining in Nevada」の詳細全文を読む スポンサード リンク
|