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Placer mining is the mining of stream bed (alluvial) deposits for minerals. This may be done by open-pit or by various surface excavating equipment or tunneling equipment.
Hydraulic mining is a form of mining that uses high-pressure jets of water to dislodge rock material or move sediment. In the placer mining of gold or tin, the resulting water-sediment slurry is directed through sluice boxes to remove the gold. It is also used in mining kaolin and coal.
A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width and are characterised by a distinct 'headscarp' or 'headwall' and progress by headward erosion. Gullies are commonly related to intermittent or ephemeral water flow usually associated with localised intense or protracted rainfall events, or snowmelt. Gullies can be formed and accelerated by cultivation practices on hillslopes in farmland, and they can develop rapidly in rangelands from existing natural erosion forms subject to vegetative cover removal and livestock activity.
Gold panning, or simply panning, is a form of placer mining and traditional mining that extracts gold from a placer deposit using a pan. The process is one of the simplest ways to extract gold, and is popular with geology enthusiasts especially because of its low cost and relative simplicity.
Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing dams, dikes, and other controls for streams and shorelines; and recovering valuable mineral deposits or marine life having commercial value. In all but a few situations the excavation is undertaken by a specialist floating plant, known as a dredger.
Gold mining is the extraction of gold resources by mining. Historically, mining gold from alluvial deposits used manual separation processes, such as gold panning. However, with the expansion of gold mining to ores that are not on the surface, has led to more complex extraction processes such as pit mining and gold cyanidation. In the 20th and 21st centuries, most volume of mining was done by large corporations, however the value of gold has led to millions of small, artisanal miners in many parts of the Global South.
Gold extraction refers to the processes required to extract gold from its ores. The great majority of gold is extracted from dilute ores using a combination of chemical processes. About 2000 tons are obtained from the earth annually, plus another 300 tons from recycling.
The California Debris Commission was a federal commission created in 1893 by an act of Congress to regulate California streams that had been devastated by the sediment washed into them from gold mining operations upstream in the Sierra Nevada. It was created to mitigate the damage to natural seasonal river flow and navigation, which had been caused by the extensive use of hydraulic mining. The act was codified under Navigation in 33 U.S.C. Chapter 14. Given substantial power by Congress, the commission significantly reduced the stream damage caused.
The ancient Romans were famous for their advanced engineering accomplishments. Technology for bringing running water into cities was developed in the east, but transformed by the Romans into a technology inconceivable in Greece. The architecture used in Rome was strongly influenced by Greek and Etruscan sources.
A drywasher is a common desert mining tool for gold mining.
The Yuba Goldfields, also known as the Hammonton dredge field, is the largest gold dredge field in California. Located along the Yuba River approximately 6–12 miles (10–20 km) upstream of the town of Marysville, in Yuba County, the Hammonton dredge field was actively dredged for gold from 1904 to 1968. In total, more than one billion cubic yards of river sediment and lesser hydraulic mining debris was dredged to produce an estimated 5.14 million ounces of gold. The goldfields are noted for their otherworldly appearance, filled with roughly linear mounds of gravels, ravines, streams and turquoise-colored pools of water. From the air, the goldfields are said to resemble intestines.
Gold became highly concentrated in California, United States as the result of global forces operating over hundreds of millions of years. Volcanoes, tectonic plates and erosion all combined to concentrate billions of dollars' worth of gold in the mountains of California. During the California Gold Rush, gold-seekers known as "Forty-Niners" retrieved this gold, at first using simple techniques, and then developing more sophisticated techniques, which spread around the world.
A gold dredge is a placer mining machine that extracts gold from sand, gravel, and dirt using water and mechanical methods.
Hushing is an ancient and historic mining method using a flood or torrent of water to reveal mineral veins. The method was applied in several ways, both in prospecting for ores, and for their exploitation. Mineral veins are often hidden below soil and sub-soil, which must be stripped away to discover the ore veins. A flood of water is very effective in moving soil as well as working the ore deposits when combined with other methods such as fire-setting.
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague.
The Omai Gold Mine is located in Guyana on the north coast of South America near the west bank of the Essequibo River in the interior of the country. Access to Omai is by road from the capital of Georgetown on the coast, and from the town of Linden approximately 60 km away. There is an operational airstrip on site which can accommodate aircraft from Georgetown. Gold mining at Omai is known from at least the 1880s, and when it was developed as a large scale mine in 1992 by Cambior, the mine was the largest gold mine in the Guiana Shield and a major source of income and employment in Guyana. During the period from 1992 – 2005, Omai produced 3.7 Moz of gold at an average grade of 1.5 g/t Au from the Fennell and the Wenot open pits.
Mercury contamination in California waterways poses a threat to both the environment and human health. This naturally occurring heavy metal may be released into the environment from natural geological sources, but most commonly occurs from anthropogenic mining operations. This metal poses a threat not only for its effects on organisms, but also for difficulty of removal from waterways and the trouble in efficiently detecting it. The roots of mercury poisoning in waterways began with the historic mining of gold within California's streambed and hillsides; since the California Gold Rush, mercury has been used for gold extraction for its ability as a catalyze with the precious metal. due to the process of extraction and washing, mercury used would either be burned away as a hazardous vapor, or washed away into waterflows, resulting in widespread contamination of river and lake sediments. mercury continues to be released today through anthropogenic sources, though state and federal agencies work to manage and ban these practices and to mitigate its effect on the environmental and on people. Many water bodies in the state of California bear fish consumption advisories due to mercury content.
Legacy sediment (LS) is depositional bodies of sediment inherited from the increase of human activities since the Neolithic. These include a broad range of land use and land cover changes, such as agricultural clearance, lumbering and clearance of native vegetation, mining, road building, urbanization, as well as alterations brought to river systems in the form of dams and other engineering structures meant to control and regulate natural fluvial processes. The concept of LS is used in geomorphology, ecology, as well as in water quality and toxicological studies.
The case of Woodruff v. North Bloomfield Gravel Mining Company was a lawsuit brought to California courts in 1882 where a group of local farmers sued North Bloomfield Mining and Gravel Company over damages caused to farmland in the Central Valley. The farmers who brought the suit claimed that the company's hydraulic mining operations resulted in the disposal of excess sediment, debris, and chemicals in local rivers. Prosecutors argued that the debris raised river beds and restricted flow in the rivers leading to heavy man-made flooding. In the years prior, flooding of debris and chemicals had destroyed a large portion of the valley's agriculture.
Twangiza Mine is an open pit gold mine in South Kivu province of the Democratic Republic of the Congo (DRC) which started operations in 2012. Production has been disrupted by attacks from rebel militias.
References
- 1 2 Water and Gold: Interpreting the Landscape of Creswick Creek, Peter Davies, Susan Lawrence and Jodi Turnbull, Messmate Press Melbourne 2015 p.64
- ↑ Lawrence, Susan; Davies, Peter, (author.) (2019), Sludge : disaster on Victoria's goldfields, La Trobe University Press in conjunction with Black Inc, ISBN 978-1-76064-110-8
{{citation}}:|author2=has generic name (help)CS1 maint: multiple names: authors list (link) - ↑ Victoria. Report of the Royal Commission Appointed to Enquire Into the Best Method of Removing the Sludge From the Gold Fields: Together With Proceedings of the Commission, Minutes of Evidence, and Appendices. Melbourne: John Ferres, Government Printer, 1859.
- ↑ "David Bannear, Historic Gold Mining Sites: North East Victoria, Draft, DNRE, Melbourne, 1996". Archived from the original on 2009-08-23. Retrieved 2009-08-24.
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