Ridgeway Mine
| Location | |
|---|---|
  Ridgeway mine Location in South Carolina  Ridgeway mine Ridgeway mine (the US) | |
| Location | Ridgeway |
| State | South Carolina |
| Country | United States |
| Coordinates | 34°16′18″N 80°54′00″W / 34.271712°N 80.900048°WCoordinates: 34°16′18″N 80°54′00″W / 34.271712°N 80.900048°W |
| Production | |
| Products |
Gold Silver [1] |
| Production |
Gold: 1,500,000 ounces Silver: 900,000 ounces |
| Type | open-pit |
| Greatest depth | 420 feet (60 ft below sea level)[2] |
| History | |
| Opened | 1988 |
| Closed | 1999 |
| Owner | |
| Company | Kennecott Utah Copper |
| Website | Kennecott Ridgeway Mining Company |
The Ridgeway mine was a gold and silver open-pit mine near Ridgeway, South Carolina and operated by Kennecott Minerals. It produced 1.5 million ounces of gold and 0.9 million ounces of silver[1] in its eleven years of operation between 1988 and 1999 and was the only active gold mine in the eastern United States for most of its life.[3] The mine's two ore bodies are part of the gold-rich[4] Carolina Slate Belt rock package that runs through the upstate Piedmont foothills. The microscopic gold deposits in the ore were recovered with a carbon in leach process that dissolved the gold in cyanide followed by an electrowinning process that deposited the dissolved gold on an electric anode.[5]
History
Gold was first found in the Carolina Slate Belt in 1827[5] at the Haile mine in nearby Lancaster County. Placer mining, hydraulic mining and later use of the Newbery-Vautin chlorination process kept South Carolina mines going but by the year 1900 mining had mostly stopped.[5] In the 1960s interest in the Ridgeway area increased after John Chapman found gold in the Ridgeway area[5] while panning in nearby creeks. Amselco Minerals, a company later merged with Kennecott Minerals, began investigating Ridgeway after geologist Irving T. Kiff noticed similarities between Ridgeway's slate outcrops and outcrops at the Haile mine.[6] Kennecott Minerals began buying land for the Ridgeway mine in 1980 and began mining in 1988.[5]
Reclamation
The mine tailings are a pyrite-bearing rock which, when exposed to water and oxygen, causes acid rock drainage and environmental damage. Kennecott Ridgeway designed an impoundment for the tailings that seals them off from rainwater runoff and the atmosphere. If fresh water was allowed to run through the tailings it would constantly dissolve and oxidize the rock's sulfides so the tailings are instead kept in stagnant water that has already had a chance to fully saturate with sulfides.[1] The impoundment was created by saturating the tailings with water, mining nearby inert saprolites and clay, sending the saprolites and clay through the ore mills and pouring them over the tailing pile to create a cone over the mine tailings.[7]
The Ridgeway mine recovery has been an ecological success with minimal seepage of acid water into the environment, a stark contrast to the nearby Barite Hill and Brewer gold mines that were both declared Superfund sites after being abandoned by their owners.[8]
South Pit Lake
Both mine pits are expected to fill with water by 2020[9] and public access is planned for the reclaimed South Pit Lake.[10] Mine management hopes to create a meromictic lake, a self-regulated lake with distinct layers of water that do not mix, to minimize oxidation of sulfides and prevent toxic metals from circulating in the environment.[11]:ii A comprehensive study of the South Pit Lake's limnology was conducted from 2000 to 2004, measuring its physical, chemical and biological properties. Wind is typically the most important contributing factor to mixing in a lake[11]:4 and the South Pit Lake was found to have a poor alignment with the prevailing direction of wind in the area.[11]:100 To counteract the mixing forces of wind the lake has other properties that promote water layer stability and stratification. Its relative depth, a ratio of the lake's surface area to its depth, is around 10%, typical of other meromictic lakes.[11]:16 There are several underwater features that dissipate wave energy and reduce the strength of wind-powered seiches in the lake.[11]:119 Finally, bacteria in the lake contributed to a pycnocline by precipitating carbon, gypsum and metals out of the upper layer, lowering its density and increasing the density of the lower layer.[11]:45 The lake successfully achieved meromixis in the winter of 2001 and maintained it until the end of the study.[11]:iii
Future mining
The Strongbow Exploration company announced that it was investigating a possible new strike of gold within three miles of Rio Tinto's Ridgeway mine in 2011.[12] After releasing several press releases announcing positive test results from drilling samples[13] and the signing of property purchase option agreements with landowners[14] there has been no further communication on their Ridgeway exploration since December of 2012.
Notes
- 1 2 3 "Ridgeway Mine" (PDF). Rio Tinto. June 2013. Retrieved 21 Apr 2018.
- ↑ "KRMC - Ridgeway Mine - North Pit". Kennecott Minerals.
- ↑ "Kennecott Ridgeway Mining Company". Kennecott Minerals.
- ↑ Foley, Nora; Ayuso, Robert (2012). "Gold Deposits of the Carolina Slate Belt, Southeastern United States: Age and Origin of the Major Gold Producers" (PDF). U.S. Geological Survey. Retrieved 21 Apr 2018.
- 1 2 3 4 5 Ralph, Chris (September 2008). "Gold Deposits Of South Carolina". ICMJ. Retrieved 21 Apr 2018.
- ↑ Gillon, Kenneth A.; Spence, William H.; Duckett, Roy P.; Benson, Christopher H. "GEOLOGY OF THE RIDGEWAY GOLD DEPOSITS".
- ↑ "Current Reclamation Activities". Kennecott Minerals.
- ↑ Fretwell, Sammy (14 October 2014). "Gold's legacy: Abandoned gold mines cost SC". The State. Retrieved 21 Apr 2018.
- ↑ Ducket, Roy; Flite, Oscar P.; O'Kane, Mike (20 November 2012). "ARD Management Rio Tinto Ridgeway Gold Mine" (PDF). Rio Tinto. Retrieved 24 Apr 2018.
- ↑ "KRMC - Reclamation Q & A". Kennecott Minerals.
- 1 2 3 4 5 6 7 Flite, Oscar (December 2006). Onset and Persistence of Biogenic Meromixis in a Filling Pit Lake-A Limnological Perspective (Thesis). Clemson University.
- ↑ "Strongbow Expands Midway Gold Project and Acquires Properties Near Ridgeway Gold Mine, South Carolina" (Press release). Strongbow Exploration Inc. 23 June 2011. Retrieved 14 August 2018.
- ↑ "Strongbow Completes Sonic Drilling Programs in South Carolina Drills 28.96 m Grading 0.97 g/t Au at Ridgeway" (Press release). Strongbow Exploration Inc. 26 June 2012. Retrieved 14 August 2018.
- ↑ "Drilling Completed at Strongbow's Shovelnose Gold Property, BC" (Press release). Strongbow Exploration Inc. 10 December 2012. Retrieved 14 August 2018.
References
Duckett, Roy. "The Kennecott Ridgeway Mine a Case Study in Sustainable Development" (pdf). Kennecott Minerals Company. Retrieved 14 August 2018.
Duckett, R.; O'Kane, M. (2006). "Hydraulic Placement Of A Dry Cover System - Design And Performance Monitoring Of The Kennecott Ridgeway Mine Tailings Dam Cover System" (PDF). Journal American Society of Mining and Reclamation. 2006: 539–554. doi:10.21000/JASMR06020539.
Press
Applebome, Peter (5 June 1991). "Striking Gold and Fear in S. Carolina". The New York Times. Retrieved 21 Apr 2018.
Velasco, Eric (5 December 1999). "Last rush for gold comes to end in S.C. Mine shifting to reclamation". The State. Retrieved 21 Apr 2018.
Natural sciences
Gillon, Kenneth A.; Spence, William H.; Duckett, Roy P.; Benson; Christopher J. (1 January 1995). "Geology of the Ridgeway Gold Deposits, Ridgeway, South Carolina". In Kyle, Richard; Crowe, Douglas E. Selected Mineral Deposits of the Gulf Coast and Southeastern United States. pp. 53–87. doi:10.5382/GB.24. ISBN 9781934969779.
Fatal accidents
Verdier, Harry L.; Underwood, Bobby A. (20 February 1997). "Fatal Powered Haulage Accident". United States Department of Labor Mine and Safety and Health Administration.
Secretary of Labor, Mine and Safety and Health Administration (MSHA) v. Fluor Daniel Incorporated, 00626-05502 A.C. Docket No. SE 94-92-M (Federal Mine and Safety and Health Review Commission 5 October 1994).