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Alluvial placers are those formed in river or stream sediments. Another name for alluvial placers are stream placers. [2] Typical locations for alluvial gold placer deposits are on the inside bends of rivers and creeks; in natural hollows; at the break of slope on a stream; the base of an escarpment, waterfall or other barrier. Stream placers ...
Because the gold in the California gravel beds was so richly concentrated, the early forty-niners simply panned for gold in California's rivers and streams, a form of placer mining. [ 10 ] [ 11 ] However, panning cannot take place on a large scale, and industrious miners and groups of miners graduated to placer mining " cradles " and "rockers ...
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 ...
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 867,000 troy ounces (27,000 kg), less than one-quarter of peak production.
It was discovered in the early 1850s, during the California gold rush. The California Mother Lode is a zone from 1.5 to 6 kilometres (0.93 to 3.73 mi) wide and 190 kilometres (120 mi) long, between Georgetown on the north and Mormon Bar on the south. The Mother Lode coincides with the suture line of a terrane, the Smartville Block. [4]
Placer County (/ ˈ p l æ s ər / PLASS-ər; Placer, Spanish for "sand deposit"), officially the County of Placer, is a county located in the U.S. state of California. As of the 2020 United States census, the population was 404,739. [4] The county seat is Auburn. [5] Placer County is included in the Greater Sacramento metropolitan area.
The oldest rocks in California date back 1.8 billion years to the Proterozoic and are found in the San Gabriel Mountains, San Bernardino Mountains, and Mojave Desert.The rocks of eastern California formed a shallow continental shelf, with massive deposition of limestone during the Paleozoic, and sediments from this time are common in the Sierra Nevada, Klamath Mountains and eastern Transverse ...
Placer gold deposits form via gravity, with the density of gold causing it to sink into trap sites within the river bed, or where water velocity drops, such as bends in rivers and behind boulders. Often placer deposits are found within sedimentary rocks and can be billions of years old, for instance the Witwatersrand deposits in South Africa ...