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251:), usually by digging and blasting to follow and remove veins of the gold-bearing quartz. By 1851, quartz mining had become the major industry of Coloma. Once the gold-bearing rocks were brought to surface, the rocks were crushed and the gold separated, either using separation in water, using its density difference from quartz sand, or by washing the sand over copper plates coated with
19:
212:
sluices, with the gold settling to the bottom where it was collected. By the mid-1880s, it is estimated that 11 million ounces (340 t) of gold (worth approximately US$ 15 billion at
December 2010 prices) had been recovered by "hydraulicking". This style of hydraulic mining later spread around the world.
185:" and "rockers" or "long-toms" to process larger volumes of gravel. Miners would also engage in "coyoteing". This method involved digging a shaft 6 to 13 meters (20 to 43 ft) deep into placer deposits along a stream. Tunnels were then dug in all directions to reach the richest veins of pay dirt.
211:
was used on ancient gold-bearing gravel beds on hillsides and bluffs in the goldfields. In a modern style of hydraulic mining first developed in
California, a high-pressure hose directed a powerful stream or jet of water at gold-bearing gravel beds. The loosened gravel and gold would then pass over
153:
The
California mountains rose and shifted several times within the last fifty million years, and each time, old streambeds moved and were dried out, leaving the deposits of gold resting within the ancient gravel beds where the gold had been collecting. Newer rivers and streams then developed, and
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and crumbled, and the exposed gold and other materials were carried downstream by water. Because gold is denser than almost all other minerals, this process further concentrated the gold as it sank, and pockets of gold gathered in quiet gravel beds along the sides of old rivers and streams.
54:
85:
and minerals (including gold) onto the sea floor; sometimes enough that islands were created. Between 400 million and 200 million years ago, geologic movement forced the sea floor and these volcanic islands and deposits eastwards, colliding with the
117:
and other mountains in
California today. As the hot magma cooled, solidified, and came in contact with water, minerals with similar melting temperatures tended to concentrate together. As the magma solidified, gold became concentrated within hydrous
283:. Previously interpreted as precursory activity to the 1906 earthquake, they have been found to have a strong seasonal pattern and due to large seasonal sediment loads in coastal bays that overlie faults as a result of mining of gold inland.
41:, 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
239:
technology (also invented in
California) had become economical, and it is estimated that more than 20 million ounces (620 t) were recovered by dredging (worth approximately US$ 28 billion at December 2010 prices).
656:
226:
After the Gold Rush had concluded, gold recovery operations continued. The final stage to recover loose gold was to prospect for gold that had slowly washed down into the flat river bottoms and sandbars of
California's
590:. The bedrock was then attacked using fire and mechanical means, and volumes of water were used again to remove debris, and to process the resulting ore. Examples of this Roman mining technology may be found at
223:, and other pollutants went into streams and rivers. As of 1999 many areas still bear the scars of hydraulic mining, since the resulting exposed earth and downstream gravel deposits do not support plant life.
534:
system. The term "ounces" used in this article to refer to gold typically refers to troy ounces. There are some historical uses where, because of the age of the use, the intention is ambiguous.
259:). Loss of mercury in the amalgamation process was a source of environmental contamination. Eventually, hard-rock mining wound up becoming the single largest source of gold produced in the
141:
As the Sierra Nevada and other mountains in
California were forced upwards by the actions of tectonic plates, the solidified minerals and rocks were raised to the surface and subjected to
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45:, 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.
920:
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Geologic evidence indicates that over a span of at least 400 million years, gold that had been widely dispersed in the Earth's crust became more concentrated by
610:. There is, however, no evidence of the earlier use of hoses, nozzles and continuous jets of water in the manner developed in California during the Gold Rush.
602:. The gold recovered using these methods was used to finance the expansion of the Roman Empire. Hushing was also used in lead and tin mining in Northern
161:
first focused their efforts on these deposits of gold, which had been gathered in the gravel beds by hundreds of millions of years of geologic action.
586:
above gold-bearing areas, and released the stored water in a flood so as to remove over-burden and expose gold-bearing bedrock, a process known as
73:-bearing regions of California. Only gold that is concentrated can be economically recovered. Some 400 million years ago, rocks that would be
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109:). Being lighter and hotter than the ancient continental crust above it, this magma forced its way upward, cooling as it rose to become the
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gravel beds was so richly concentrated, the early forty-niners simply panned for gold in
California's rivers and streams, a form of
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181:. However, panning cannot take place on a large scale, and industrious miners and groups of miners graduated to placer mining "
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A golden state: mining and economic development in Gold Rush
California (California History Sesquicentennial Series, 2)
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263:. The total production of gold in California from then until now is estimated at 118 million ounces (3700 t).
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In the most complex placer mining, groups of prospectors would divert the water from an entire river into a
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alongside the river, and then dig for gold in the newly exposed river bottom. Modern estimates by the
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Both during the Gold Rush and in the decades that followed, gold-seekers also engaged in "hard-rock"
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some of these cut through the old channels, carrying the gold into still larger concentrations.
657:"Amador City, California – Historic Gold Mining Town. [full text] [book links]"
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onto western North
America to build California lay at the bottom of a large sea. Subsea
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Use of volumes of water in large-scale gold-mining dates at least to the time of the
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247:, that is, extracting the gold directly from the rock that contained it (typically
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system is traditionally used to measure precious metals, not the more familiar
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746:"Seasonal Seismicity of Northern California Before the Great 1906 Earthquake"
200:) of gold were removed in the first five years of the Gold Rush (worth over
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forced the sea floor beneath the American continental mass. As it sank, or
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A byproduct of these extraction methods was that large amounts of gravel,
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Charles N. Alpers; Michael P. Hunerlach; Jason T. May; Roger L. Hothem.
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readme-ebooks.org, The Pierian Press, 8 August 1999. Online. Internet
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Images and detailed description of placer mining tools and techniques
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The age of gold: the California Gold Rush and the new American dream
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The age of gold: the California Gold Rush and the new American dream
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697:"Mercury Contamination from Historical Gold Mining in California"
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Goldfields in the mountains of northern and central California.
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Rawls, James J. and Orsi, Richard (eds.) (1999), pp. 116–121.
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Rawls, James J. and Orsi, Richard (eds.) (1999), pp. 39–43.
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Rawls, James J. and Orsi, Richard (eds.) (1999), pp. 36–39.
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Rawls, James J. and Orsi, Richard (eds.) (1999), pp. 32–36.
275:, more than at any other time in the historical record for
497:. Norman: University of Oklahoma Press. pp. 110–111.
425:. Norman: University of Oklahoma Press. pp. 108–110.
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rising after being subducted under the continental crust.
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Rawls, James J. and Orsi, Richard (eds.) (1999), p. 199.
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Rawls, James J. and Orsi, Richard (eds.) (1999), p. 90.
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Rawls, James J. and Orsi, Richard J. (eds.) (1999).
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and other gold-bearing areas of California (such as
30:, similar to what the early miners would have found.
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105:heated and melted, producing large molten masses (
724:"California – Gold, Geology & Prospecting"
551:Mining History and Geology of the Mother Lode
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93:Beginning about 200 million years ago,
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204:16 billion at December 2010 prices).
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919:CS1 maint: multiple names: authors list (
483:Bancroft, Hubert Howe (1888), pp. 87–88.
235:in Siskiyou County). By the late 1890s,
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122:solutions and was deposited within
821:The works of Hubert Howe Bancroft,
814:Bancroft, Hubert Howe (1884–1890)
582:. Roman engineers built extensive
445:Brands, H. W. (2003), pp. 198–200.
14:
792:
798:Presentation by H.W. Brands on
411:Hill, Mary (1999), pp. 105–110.
390:Hill, Mary (1999), pp. 169–173.
884:University of California Press
861:University of California Press
399:Hill, Mary (1999), pp. 94–100.
381:Hill, Mary (1999), pp. 174–78.
327:Hill, Mary (1999), pp. 168–69.
305:University of California Press
90:, which was moving westwards.
37:became highly concentrated in
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663:. 18 May 1743. Archived from
372:Hill, Mary (1999), pp. 149–58
281:1906 San Francisco earthquake
145:. The surrounding rock then
882:. Berkeley and Los Angeles:
859:. Berkeley and Los Angeles:
560:(accessed October 16, 2006).
303:. Berkeley and Los Angeles:
271:There were decades of minor
207:In the next stage, by 1853,
750:Pure and Applied Geophysics
569:Starr, Kevin (2005), p. 89.
28:Tuolumne County, California
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857:Gold: the California story
318:Hill, Mary (1999), p. 168.
301:Gold: the California story
255:(with which gold forms an
113:rock found throughout the
970:Gold in the United States
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584:aqueducts and reservoirs
267:Geological after-effects
157:The Forty-Niners of the
493:Young, Otis E. (1970).
421:Young, Otis E. (1970).
348:. New York: Doubleday.
816:History of California,
702:U.S. Geological Survey
556:June 17, 2006, at the
194:U.S. Geological Survey
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932:California: a history
928:Starr, Kevin (2005).
828:Brands, H.W. (2003).
744:Westaway, R. (2002).
340:Brands, H.W. (2003).
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975:California Gold Rush
965:Mining in California
823:complete text online
802:, September 19, 2002
159:California Gold Rush
88:North American Plate
43:California Gold Rush
855:Hill, Mary (1999).
762:2002PApGe.159....7W
667:on November 6, 2018
466:image of a long tom
299:Hill, Mary (1999).
277:Northern California
938:The Modern Library
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729:19 February
671:6 September
592:Las Médulas
528:Troy weight
273:earthquakes
959:Categories
780:References
708:2008-02-26
596:Dolaucothi
175:California
81:deposited
39:California
902:cite book
838:Doubleday
598:in South
147:weathered
99:subducted
79:volcanoes
608:Cornwall
554:Archived
469:Archived
458:Archived
237:dredging
75:accreted
67:geologic
758:Bibcode
604:Britain
588:hushing
309:p. 167.
257:amalgam
253:mercury
183:cradles
173:in the
143:erosion
111:granite
49:Geology
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249:quartz
245:mining
190:sluice
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120:silica
22:Three
600:Wales
287:Notes
124:veins
107:magma
59:magma
26:from
942:ISBN
921:link
914:help
888:ISBN
865:ISBN
842:ISBN
731:2013
673:2010
606:and
526:The
499:ISBN
427:ISBN
350:ISBN
217:silt
202:US$
171:gold
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