Gold mining in the United States

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US annual gold production, 1840-2012.

Gold mining in the United States has taken place continually since the discovery of gold at the Reed farm in North Carolina in 1799. The first documented occurrence of gold was in Virginia in 1782.[1] Some minor gold production took place in North Carolina as early as 1793, but created no excitement. The discovery on the Reed farm in 1799 which was identified as gold in 1802 and subsequently mined marked the first commercial production. .[2]

The large scale production of gold started with the California Gold Rush in 1848.

The closure of gold mines during World War II by the War Production Board Limitation Order No. 208 in autumn 1942 was a major impact on the production until the end of the war. [3]

US gold production greatly increased during the 1980s, due to high gold prices and the use of heap leaching to recover gold from disseminated low-grade deposits in Nevada and other states.

In 2012 the United States produced 230 tonnes of gold, making it the third-largest gold-producing nation, behind China and Australia.[4] Most gold produced today in the US comes from large open-pit heap leach mines in the state of Nevada. The US is a net exporter of gold.[5]

Gold mining by state[edit]

Alabama[edit]

Gold was discovered in Alabama about 1830, shortly following the Georgia Gold Rush. The principal districts were the Arbacoochee district in Cleburne County, mostly from placer deposits, and the Hog Mountain district in Tallapoosa County, which produced 24 thousand troy ounces (750 kg) from veins in schist.[6]

Alaska[edit]

Main article: Gold mining in Alaska

Russian explorers discovered placer gold in the Kenai River in 1848, but no gold was produced. Gold mining started in 1870 from placers southeast of Juneau.[7] Today, most gold production in Alaska is from the Fort Knox mine, a large open pit and cyanide leaching operation in the Fairbanks mining district. The Fort Knox mine produced 333 thousand troy ounces (10.3 tonnes) of gold in 2006. Alaska produced a total of 40.3 million troy ounces of gold from 1880 through the end of 2007.

Arizona[edit]

Arizona has produced more than 16 million troy ounces (498 tonnes) of gold.

Gold mining in Arizona reportedly began in 1774 when Spanish priest Manuel Lopez directed Papago Indians to wash gold from gravel on the flanks of the Quijotoa Mountains, Pima County. Gold mining continued there until 1849, when the Mexican miners were lured away by the California Gold Rush. Other gold mining under Spanish and Mexican rule took place in the Oro Blanco district of Santa Cruz County, and the Arivaca district, Pima County.[8]

Mountain man Pauline Weaver discovered placer gold on the east side of the Colorado River in 1862. Weaver's discovery started a gold rush to the now ghost town of La Paz, Arizona.

The gold-bearing quartz veins of the Vulture Mine, southwest of Wickenburg, in Maricopa County were discovered in 1863. The mine produced 366 thousand ounces of gold through 1959.[9]

Gold Road mine, Oatman, Arizona.

The San Francisco district, which includes the towns of Oatman, Bullhead City and Katherine in Mohave County was discovered in 1863 or 1864, but saw little activity until a rush to the district occurred in 1902. The district produced 2.0 million ounces of gold through 1959.[10]

The last gold mine to operate in Arizona was the Gold Road mine at Oatman, which shut down in 1998. Patriot Gold is exploration drilling at the Moss mine at Oatman.[11] Columbus Gold is currently doing exploration drilling for gold at four prospects in western Arizona.

In 2006, all of Arizona's gold production came as a byproduct of copper mining.

California[edit]

Main article: Gold in California

Spanish prospectors discovered gold in the Potholes district between 1775 and 1780, along the Colorado River, in present Imperial County, California, about ten miles northeast from Yuma, Arizona. The gold was recovered from dry placers. Other placer deposits on the west bank of the Colorado River were quickly discovered, including the Picacho and Cargo Muchacho districts.

Placer gold deposits were discovered at San Ysidro in San Diego County in 1828, San Francisquito Canyon and Placerita Canyon in Los Angeles County in 1835 and 1842, respectively

Gold miners excavate a gold-bearing bluff with jets of water at a placer mine in Dutch Flat, California sometime between 1857 and 1870.

Major gold mining in California started in 1848 during the California Gold Rush.Gold was found by James Marshall at Sutters Mill, property of John Sutter, in now a days Coloma. In 1849, people started hearing about the gold and after just a few years San Francisco's population was up by thousands. Gold production in California peaked in 1852, at 3.9 million troy ounces (121 tonnes) produced in that year. But the placer deposits worked in the early years were quickly exhausted, and production crashed. Hardrock mining (in California called quartz mining) began in 1849, and placer mining by hydraulic mining began in 1852. Despite the new mining methods, by 1865 production was 867 thousand troy ounces (27 tonnes), less than one-quarter of peak production.

Production sank to 412 thousand troy ounces (12.8 tonnes) in 1929, but then soared to more than 1.4 million troy ounces (43.5 tonnes) for each year 1939 through 1941, after the price was raised from $20.67 to $35 per ounce. However, the federal government, in War Production Board Order L-208, ordered gold mines closed, to free up resources for the war effort during World War II, and production fell to 148 thousand troy ounces (4.6 Fes) in 1943. Post-war gold production never reached the peak of the early 1940s, as inflation and the fixed price of gold eroded its value.[12]

The largest gold-mining district in California is the famous Mother Lode of the Sierra Nevada. Discovered in the early 1850s, the lode is a zone one to four miles wide and running 120 miles northwest-southeast from El Dorado County in the north, through Amador, Calaveras, and Tuolumne counties, to Mariposa County in the south. The gold of the Mother Lode is in quartz veins within phyllite, schist, slate, and greenstone. Through 1959, the Mother Lode produced about 13.3 million troy ounces (414 tonnes) of gold.[13]

The second-largest gold-mining district in California was Grass Valley-Nevada City district in Nevada County. Gold in Holocene gravels was discovered in 1850, followed a few years later by hydraulic mining of Tertiary gravels. By 1880, most of the mining had shifted to lode deposits, such as the Empire Mine. Through 1959, the district produced 10.4 million troy ounces (323 tonnes) of lode gold, and 2.2 million troy ounces (68.4 tonnes) of placer gold.[14]

The rich placer deposits of the Columbia Basin-Jamestown-Sonora district were discovered in 1853. Almost all the gold was found at the base of Quaternary gravels, but some drift mines were worked in Tertiary gravels. Total production was about 5.9 million troy ounces (183 tonnes) of gold.[15]

In 2007, California produced 9,400 ounces (1603 kg) of gold from two mines. The Mesquite mine in Imperial County restarted active mining in 2007, having been inactive since 2001; now owned by New Gold, it produces more than 100,000 ounces (3.1 t) of gold per year.[16] The only other gold producer in the state, the Briggs mine in Inyo County stopped mining in 2004, but continues to produce small amounts of gold from the leach pads, from previously mined ore.[17]

Emgold Mining is going through the permitting process to reopen the Idaho Maryland gold mine at Grass Valley, Nevada County.

Colorado[edit]

Gold was discovered in 1858 during the Pike's Peak Gold Rush in the vicinity of present-day Denver in 1858, but the deposits were small. The first important gold discoveries in Colorado were in the Central City-Idaho Springs district in January 1859. Three Colorado mines continue to produce gold. The Cripple Creek & Victor Gold Mine at Victor, an open-pit heap leach operation owned by AngloGold Ashanti, is the leading producer, with 283 thousand troy ounces (8.8 tonnes) of gold in 2006. Other active gold mines in the state are underground Golden Wonder mine near Lake City, and the Cash and Rex mines in the Gold Hill mining district in Boulder County, Colorado.[18]

Florida[edit]

Small amounts of gold were mined commercially in North Eastern Florida during the late 19th Century, at the site where Mike Roess Gold Head Branch State Park is located today. No records are extant on the amount of gold produced, but the find was insufficient to keep the operation running commercially, and the small amount of pay dirt was depleted within a matter of months.[19]

Georgia[edit]

Georgia is credited with a total historical production of 871 thousand ounces of gold from 1830 through 1959.[20] Although an historically important gold producer, the state does not presently produce any gold commercially.

See also:

Idaho[edit]

Gold was first discovered in Idaho in 1860, in Pierce at the juncture where Canal Creek meets Orofino Creek.

The leading historical gold-producing district is the Boise Basin in Boise County, which was discovered in 1862 and produced 2.9 million troy ounces (90.2 tonnes), mostly from placers.[21]

The French Creek-Florence district in Idaho County began in the 1860s, and has produced about 1 million troy ounces (31 tonnes) from placers.

The Silver City district in Owyhee County began producing in 1863, and made over 1 million troy ounces (31 tonnes), mostly from lode deposits.

The Coeur d’Alene district in Shoshone County has made 440 thousand troy ounces (13.7 tonnes) of gold as byproduct to silver mining.[22]

In 2006, active gold mines in Idaho included the Silver Strand mine and the Bond mine.[23]

Maryland[edit]

Gold was reported in Maryland as early as 1830, but no production resulted. Placer gold was discovered at Great Falls near Washington, DC in 1861 during the American Civil War by Union soldiers from California. After the war a number of mines were opened on gold-bearing quartz veins in Montgomery County. No gold production has been reported since 1951. Total production was about 6 thousand troy ounces (190 kg).[24]

Michigan[edit]

Approximately 29 thousand troy ounces (900 kg) of gold were produced from the Ropes gold mine northeast of Ishpeming in Marquette County, Michigan. The underground mine, originally operated from 1880 to 1897, and reopened from 1983–1989,[25] extracted gold from quartz veins in peridotite.[26]

Montana[edit]

Gold was first discovered in Montana in 1852, but mining did not begin until 1862, when gold placers were discovered at Bannack, Montana in 1862. The resulting gold rush resulted in more placer discoveries, including those at Virginia City in 1863, and at Helena and Butte in 1864.[27] In 1867, the Atlantic Cable Quartz Lode was located.

The Butte district, although mined primarily for copper, produced 2.9 million ounces (91 tones) of gold through 1990, almost all as a byproduct of copper production.[28]

Current active hardrock gold mines include the Montana Tunnels mine, and the Golden Sunlight mine. Active gold placers include the Browns Gulch placer and the Confederate Gulch placer. Gold is also produced from three platinum mines in the Stillwater igneous complex: the Stillwater mine, the Lodestar mine, and the East Boulder Project.[29]

Nevada[edit]

Main article: Gold mining in Nevada

Nevada is now the leading gold-producing state in the nation, in 2007 producing 80% of the gold mined in the United States.[5] 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 Jerritt Canyon and the Getchell Mine.

Newmont Mining Corporation and Barrick Gold Corporation operate several large mines on the prolific Carlin Trend or Carlin Unconformity, which is one of the worlds richest mining districts. Gold Standard Ventures is currently exploring the Railroad project on the southern portion of the Carlin Trend, within the historic Bullion Mining District.

New Mexico[edit]

Gold was first discovered in New Mexico in 1828 in the “Old Placers” district in the Ortiz Mountains, Santa Fe County, New Mexico. The placer gold discovery was followed by discovery of a nearby lode deposit.[30]

In 1877, two prospectors collected float in the area of the future Opportunity Mine near Hillsboro, New Mexico, which was assayed at $160 per ton in gold and silver. Soon, ore was discovered at the nearby Rattlesnake vein and a placer deposit of gold was found in November at the Rattlesnake and Wicks gulches. Total production prior to 1904 was about $6,750,000.[31]

In 2007 all gold production in New Mexico (13 thousand troy ounces) came as a byproduct of hopper mining from two large open pit mines in Grant County. However, two primary gold mines are being readied for production: the Northstar mine in Rio Arriba County, and the San Lorenzo Claims mine in Socorro County.[32]

North Carolina[edit]

Main article: Carolina Gold Rush

North Carolina was the site of the first gold rush in the United States, following the discovery of a 17 pound (7.7 kg) gold nugget by 12-year old Conrad Reed in a creek at his father’s farm in 1799. The Reed Gold Mine, southwest of Georgeville in Cabarrus County, North Carolina produced about 50 thousand troy ounces (1.6 tonnes) of gold from lode and placer deposits.[33]

Gold was produced from 15 districts, almost all in the Piedmont region of the state. Total gold production is estimated at 1.2 million troy ounces (37.3 tonnes).

Oregon[edit]

Although gold mines are spread over much of Oregon, almost all of the gold produced has come from two principal areas: the Klamath Mountains in southwest Oregon, including Coos, Curry, Douglas, Jackson and Josephine counties; and the Blue Mountains in northeast Oregon, mostly in Baker and Grant counties.

Prospectors from Illinois discovered placer gold in the Klamath Mountains of southwest Oregon in 1850, starting a rush to the area. Lode gold deposits were also discovered.

Travellers along the Oregon Trail bound for the Willamette Valley are said to have discovered gold in northeastern Oregon in 1845, but mining in earnest did not begin until 1861.[34]

The 2013 television show Ghost Mine involved gold miners in Sumpter, Oregon.

Pennsylvania[edit]

About 37 thousand troy ounces (1.2 tonnes) of gold was produced from the Cornwall iron mine five miles south of Lebanon, Lebanon County, Pennsylvania. Although the deposit produced iron since 1742, no gold was reported from the mine until 1878.[35]

South Carolina[edit]

Gold mines in the Carolina Slate Belt - USGS.

South Carolina had a number of lode gold mines along the Carolina Slate Belt.[36]

The Haile deposit was discovered in Lancaster County in 1827, and at least 275 thousand ounces of gold were extracted intermittently between then and 1942, when the gold mine was ordered closed as nonessential to the war effort. Beginning in 1951, the deposit was mined for associated sericite, which was used as a white filler.[37] Gold is associated with silicic, kaolinitic, and pyritic alteration of greenschist-grade felsic metavolcanics.[38] The mine was reopened as an open pit in the 1980s, and operated until 1992. Kinross Gold Corporation's reclamation of the Haile site was nominated for a US Bureau of Land Management "Hardrock Mineral Environmental Award."

The Brewer mine operated from 1828 to 1995, and is now a federal Superfund site.[39]

Kennecott Minerals operated the Ridgeway open-pit gold mine from 1988 to 1999, and the land is now being reclaimed by Kennecott.

The Barite Hill mine operated from 1990 to 1994.

South Dakota[edit]

Main article: Black Hills Gold Rush

The only operating gold mine in South Dakota is the Wharf mine, an open pit heap leach operation.[40]

Tennessee[edit]

Placer gold was discovered on Coker Creek in Monroe County, Tennessee in 1827. The district produced about 9 thousand troy ounces (300 kg).[41]

About 15 thousand troy ounces (450 kg) of gold was recovered from the massive sulfide copper ores at Ducktown, Tennessee.

Texas[edit]

Some prospects have been excavated for gold on the Llano Uplift of central Texas. Gold prospects include the Heath mine and the Babyhead district, both in Llano County, and the Central Texas mine in Gillespie County. Gold production, if any, is not known.[42] Historically, the Lost Nigger Gold Mine may be in Texas.

Utah[edit]

Most gold produced in Utah today is a byproduct of the huge Bingham Canyon copper mine, southwest of Salt Lake City. In 2006, the Bingham Canyon mine produced 16.3 tonnes of gold, making it the fourth-largest gold producer in the US.[43] Over its life, Bingham Canyon has produced more than 23 million ounces (715 tonnes) of gold.

The Barneys Canyon mine in Salt Lake County, the last primary gold mine to operate in Utah, stopped mining in 2001, but is still recovering gold from its heap leaching pads. Utah gold production was 460 thousand troy ounces (14 tonnes) in 2006.[44]

Virginia[edit]

Washington[edit]

Gold was first discovered in Washington in 1853, as placer deposits in the Yakima Valley. Production from the state never exceeded 50,000 troy ounces per year until the mid-1930s, when large hard rock deposits were developed near the Chelan Lake and Wenatchee deposits in Chelan County, and the Republic deposit in Ferry County. Production through 1965 is estimated to be 2.3 million ounces.[45]

Wyoming[edit]

Gold was discovered at the South Pass-Atlantic City-Sweetwater district in present Fremont County in 1842. The placers were worked intermittently until 1867, when the first important gold vein was discovered, and prospectors and miners rushed to the area.. The towns of South Pass City, Atlantic City, and Miner's Delight catered to the miners. The district was nearly deserted by 1875, and was worked only intermittently afterward. Total gold production was about 300 thousand troy ounces (9.3 tonnes). In 1962, the district became the site of a major iron mine.[46]

Moraine gold[edit]

Several states (e.g., Illinois, Indiana, Ohio, Pennsylvania) have placer gold deposits, despite having no hard rock gold deposits. This placer gold is found north of, or near the terminus of, Pleistocene, or earlier, moraines left by Ice Age glaciers that pushed gold-rich dirt down from Canada, where hard rock gold deposits do exist, and which were scoured by glaciers. Small commercial operations have existed at various times, to mine this gold, with various degrees of limited success. The southernmost limit of these moraines, Pleistocene and older, is approximately at the Ohio River for Illinois, Indiana, and Ohio.[47][48][49] The moraines in Pennsylvania are in the northwestern and northeastern portions of the Commonwealth.[50]

Controversy[edit]

Many western US gold mines are located on federal public land, on which the mining companies pay no royalties to the US government. Gold mines operate under the General Mining Act of 1872, which permits mineral mining on public land without payment of royalties. Fighting reforms to have the gold mining industry pay royalties, the local community commission in Elko County, Nevada said that royalties would force mining companies to cut jobs and move elsewhere.[51]

The National Mining Association (NMA), the official voice of the mining industry in Washington D.C., supports a net income production payment or royalty system for minerals produced on federal lands. NMA believes that this system would strike the proper balance between providing the public with a fair return while nurturing domestic mining operations.[52]

See also[edit]

References[edit]

  1. ^ A.H. Koschmann and Bergendahl, 1968, Principal Gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.253.
  2. ^ A.H. Koschmann and Bergendahl, 1968, Principal Gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.211.
  3. ^ Craig, James R; Rimstidt, J.Donald (1998). "Gold production history of the United States". Ore Geology Reviews 13 (6): 407. doi:10.1016/S0169-1368(98)00009-2. 
  4. ^ US Geological Survey, Mineral Commodities Summary (2013): Gold PDF file, retrieved 29 January 2013.
  5. ^ a b Mining review, Mining Engineering, May 2007, p.28.
  6. ^ A.H. Koschman and M.H. Bergendahl (1968) Principal Gold-Producing Districts of the United States, U.S. Geological Survey, Professional Paper 610, p.6-8.
  7. ^ A.H. Koschman and M.H. Bergendahl (1968) Principal Gold-Producing Districts of the United States, U.S. Geological Survey, Professional Paper 610, p.8.
  8. ^ Maureen G. Johnson, 1972, ''Gold Placer Deposits of Arizona, US Geological Survey, Bulletin 1355.
  9. ^ A. H. Koschmann and M. H. Bergendahl, Principal Gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.40.
  10. ^ A. H. Koschmann and M. H. Bergendahl, Principal Gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.40-41.
  11. ^ http://www.admmr.state.az.us/Publications/ofr07-24.pdf
  12. ^ William B. Clark (1970) Gold districts of California, California Division of Mines and Geology, Bulletin 193, p.4.
  13. ^ A.H. Koschmann and M.H. Bergendahl (1968)Principal Gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.55-56.
  14. ^ A.H. Koschmann and M.H. Bergendahl (1968)Principal Gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.70-71.
  15. ^ A.H. Koschmann and M.H. Bergendahl (1968)Principal Gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.82-83.
  16. ^ "First Bucyrus branded MT3700 goes into service at the New Gold Mesquite Mine in California," Mining Engineering, October 2010, p.15.
  17. ^ S. Kohler, California, Mining Engineering, May 2008, p.78.
  18. ^ J. Burnell and others, Colorado, Mining Engineering, May 2007, p.76-77.
  19. ^ Placard at Mike Roess Gold Head Branch State Park.
  20. ^ A. H. Koschmann and M. H. Bergendahl, 1968, Principal Gold-Producing Districts of the United States, US Geological Survey, Professional paper 610, p.119.
  21. ^ A.H. Koschman and M.H. Bergendahl (1968) Principal Gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.124-125.
  22. ^ M. H. Bergendahl (1964) Gold, in Mineral and Water Resources of Idaho, Idaho Bureau of Mines and Geology, Special Report No. 1, p.93-101.
  23. ^ V. S. Gillerman and others, Idaho, Mining Engineering, May 2007, p.83.
  24. ^ Emery T. Cleaves (1964) Mineral resources of Montgomery and Howard Counties, in Howard and Montgomery Counties, Maryland Geological Survey, p.264-266.
  25. ^ Ropes Mine, Ishpeming, Marquette Co., Michigan, USA, mindat.org, 2010, accessed 2010-10-12.
  26. ^ A.H. Koschman and M.H. Bergendahl (1968) Principal Gold-Producing Districts of the United States, U.S. Geological Survey, Professional Paper 610, p.141-142.
  27. ^ A. H. Koschman and M. H. Bergendahl (1968) Principal gold-Producing Districts of the United States, US Geological Survey, Professional Paper 610, p.143.
  28. ^ Edwin W. Tooker, 1990, "Gold in the Butte district, Montana," in Gold in Porphyry Copper Systems, US Geological Survey, Bulletin 1857-E, p.E19
  29. ^ R. McCullough, Montana, Mining Engineering, May 2007, p.95.
  30. ^ Fayette Jones (1905) New Mexico Mines and Minerals, reprinted as Old Gold Mines and Ghost Camps of New Mexico, Fort Davis, Tex.: Frontier Book Co., p.21-23.
  31. ^ Harley, George Townsend, The Geology and Ore Deposits of Sierra County, New Mexico, New Mexico State Bureau of Mines and Mineral Resources Bulletin 10, 1934, pp 139-140
  32. ^ S.A. Lucas Kamat, "New Mexico," Mining Engineering, May 2008, p.111.
  33. ^ A.H. Koschman and M.H. Bergendahl (1968) Principal Gold-Producing Districts of the United States, U.S. Geological Survey, Professional Paper 610, p.212.
  34. ^ Howard C. Brooks and Len Ramp (1968) Gold and Silver in Oregon, Oregon Department of Geology and Mineral Industries, Bulletin 61.
  35. ^ A.H. Koschman and M.H. Bergendahl (1968) Principal Gold-Producing Districts of the United States, U.S. Geological Survey, Professional Paper 610, p.231.
  36. ^ US Geological Survey: Carolina Slate Belt Gold Deposits
  37. ^ Jeffrey C. Wynn and Robert W. Luce, Geophysical methods as mapping tools in a strata-bound gold deposit: Haile mine, Carolina slate belt, Economic Geology, March April 1984, p.383-388.
  38. ^ W.H. Spence and others, Origin of the gold mineralization at the Haile mine, Lancaster County, South Carolina, Mining Engineering, January 1980, p.70-73.
  39. ^ Brewer Gold Mine NPL Site Summary - Land Cleanup and Wastes | Region 4 | US EPA
  40. ^ E. H. Holm and others, South Dakota, Mining Engineering, May 2007, p.111.
  41. ^ A.H. Koschman and M.H. Bergendahl (1968) Principal Gold-Producing Districts of the United States, U.S. Geological Survey, Professional Paper 610, p.240.
  42. ^ Edgar B. Heylman, Gold in Texas, International California Mining Journal, October 2001.
  43. ^ US Geological Survey, 2006 Minerals Yearbook, p.313, PDF file, retrieved 3 January 2009.
  44. ^ R.L. Bon and K.A. Krahulec, Utah, Mining Engineering, May 2007, p.116.
  45. ^ A.H. Koschman and M.H. Bergendahl (1968) Principal Gold-Producing Districts of the United States, U.S. Geological Survey, Professional Paper 610, p.254-255.
  46. ^ Richard W.Bayley (1969) Ore deposits of the Atlantic City District, Fremont County, Wyoming, in Ore Deposits of the United States, 1933-1967, v.1, New York: American Institute of Mining Engineers, p.589-604.
  47. ^ J.E. Lamar, Gold and Diamond Possibilities in Illinois, June 1968, http://www.isgs.uiuc.edu/education/pdf-files/gold-poss.pdf
  48. ^ Geofacts #9, Gold in Ohio, November 1995, http://www.dnr.state.oh.us/Portals/10/pdf/GeoFacts/geof09.pdf
  49. ^ Glacial Map of Ohio http://www.dnr.state.oh.us/portals/10/pdf/glacial.pdf
  50. ^ Glacial Map of Pennsylvania http://www.dcnr.state.pa.us/topogeo/maps/map59.pdf
  51. ^ NBC News, Fleecing of America, March 15, 2010, http://www.msnbc.msn.com/id/3032619/#35883250
  52. ^ NMA Document Mining Law Reform: Sensible Solutions, http://www.nma.org/pdf/072407_Mining_Law_Reform.pdf

External links[edit]

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