Placer mining
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Placer mining is the mining of stream bed deposits for minerals. This may be done by open-pit mining or by various surface excavating equipment or tunneling equipment.
19th-century miner pouring water into a rocker box which, when rocked back and forth, will help separate gold dust from the alluvium
A placer mine in Alma, Colorado in 1880
Plate depicting placer mining from the 1556 book De re metallica
Panning for gold in Korea, c. 1900
Alluvium
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Alluvium is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes
Placer mining
…frequently used for precious metal deposits (particularly gold, and platinum to a much lesser extent) 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…
Alluvium deposits in the Gamtoos Valley in South Africa
An alluvial plain in Red Rock Canyon State Park (California)
Alluvial river deposits in the Amazon basin, near Autazes, AM, Brazil. The seasonal deposits are extremely fertile and crucial to subsistence farming in the Amazon Basin along the river banks.