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Placer mining is frequently used for precious metal deposits (particularly gold) and gemstones, both of which are often found in alluvial deposits—deposits of sand and gravel in modern or ancient stream beds, or occasionally glacial deposits. The metal or gemstones, having been moved by stream flow from an original source such as a vein, are ...
The name is from the Spanish word placer, meaning "alluvial sand". Placer mining is an important source of gold, and was the main technique used in the early years of many gold rushes, including the California Gold Rush. Types of placer deposits include alluvium, eluvium, beach placers, aeolian placers and paleo-placers. [2]
During hydraulic mining when the water, slurry, and debris flowed over the sluices and drainage tunnels, the particles were also mixed with liquid mercury. [3] The mercury was used during the extraction period during the mining process. The mercury was used to attract the gold and sometimes silver from the mining ore, for extraction. [4]
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Adverse mining effects on biodiversity depend a great extent on the nature of the contaminant, the level of concentration at which it can be found in the environment, and the nature of the ecosystem itself. Some species are quite resistant to anthropogenic disturbances, while some others will completely disappear from the contaminated zone.
"Panning out" ~ Stereoscopic view of print taken by the U.S. Geological and Geographic Survey of the Territories ~ circa 1874–1879 Gold panning is a simple process. Once a suitable placer deposit is located, some alluvial deposits are scooped into a pan, where they are then wetted and loosed from attached soils by soaking, fingering, and aggressive agitation in water.
In the most complex placer mining, groups of prospectors would divert the water from an entire river into a sluice alongside the river, and then dig for gold in the newly exposed river bottom. [15] Modern estimates by the U.S. Geological Survey are that some 12 million ounces [ 16 ] (370 t ) of gold were removed in the first five years of the ...
Secret Ravine is a perennial tributary of Miners Ravine which shortly thereafter runs into Dry Creek in Placer County, California. Its course lies within the cities of Rocklin, Loomis, and Roseville, as well as unincorporated parts of Placer County. It passes through the campus of Sierra College.