User:Hemlock Martinis/Mining in Nevada
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[edit] History
Although there were unsubstantiated claims of Spanish colonial mining in Nevada during the 1770s, the first known incident took place in 1849. A group of Mormon 49ers on their way to the California Gold Rush discovered gold in the Carson River near what is now Dayton.[1]
[edit] Modern industry
[edit] Silver
Nevada is the second largest producer of silver in the United States behind Alaska.[2]
[edit] Gold
Nevada is now the leading gold-producing state in the nation, currently producing 82% of all the gold mined in the United States.[3] 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, operate gold mines in the state. Active gold mines include those at Jerritt canyon.
Although Nevada was known much more for silver in the 1800s, many of the early silver-mining districts also produced considerable gold. The Comstock Lode, for instance, produced 8.6 million troy ounces (267 tonnes) of gold through 1959, and the Eureka district produced 1.2 million troy ounces (37.3 tonnes).
Goldfield was discovered in 1900, and began major gold production in 1902. The ore occurs in altered shear zones in Tertiary dacite and andesite. Total gold production through 1959 was 4.2 million troy ounces (131 tonnes).[4]
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 excitement. It was not until 1961 that Newmont Mining 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 then price 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.[5] The Carlin trend, 5 miles wide and 40 miles long running northwest-southeast, has since produced more gold than the any other mining district in the United States. The trend surpassed 50 million troy ounces (1,555 tonnes) 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.
[edit] Copper
The first commercial copper mining district in Nevada was at Yerington in Lyon County. The Ludwig Mine opened in 1865, but the district produced only modest amounts of copper until a railroad was built to the district in 1911, and a smelter built in 1912 at nearby Thompson. The copper ore bodies are contact metamorphic replacement deposits in limestone. Production through 1921 was 39 thousand tonnes of copper.[6].
The largest copper producer in Nevada has been the Ely district (also called the Robinson district) in White Pine County. A Native American showed mineralization to prospectors in 1867, and the district started in a small way as a lode gold producer. A railroad link in 1906 made it economically possible to start large scale open pit mining of the large porphyry copper deposits, and the first copper was produced in 1908.[7] Mining was halted in recent years due to low copper prices, but the open pit was reopened in 2004 by Quadra Mining Ltd.
[edit] Citations
- ^ [1]
- ^ Brooks, William E. (2007), Mineral Commodity Summaries: Silver, United States Geological Survey, <http://minerals.er.usgs.gov/minerals/pubs/commodity/silver/silvemcs07.pdf>. Retrieved on 5 December 2007
- ^ Mining review, Mining Engineering, May 2007, p.28.
- ^ A.H. Koschmann and M.H. Bergendahl, Principal Gold-Producing Districts of the United States, US Geological Survey, Preofessional Paper 610, p.177-178.
- ^ 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.
- ^ Francis Church Lincoln (1923) Mining Districts and Mineral Resources of Nevada, reprinted 1982, Las Vegas: Nevada Publications, p.133-134.
- ^ Francis Church Lincoln (1923) Mining Districts and Mineral Resources of Nevada, reprinted 1982, Las Vegas: Nevada Publications, p.245-246.
