Made by Arthur Barr, this short film shows some of the technologies used by prospectors to find gold in the 1849 California Gold Rush. At 2:00, a prospector shows how a pan is used to sift river sand in search of gold flakes. At 2;24 a claim is staked out with a claim post. At 3:30 a rocker or cradle is made to sift gravel. At 3:53, wooden bars called riffers and a hopper to hold the sand and gravel are created from wood. At 4:40 the operation of the hopper is shown. At 6:17 a Long Tom sluice is shown, which used the power of the river to separate the sand and gold from the gravel, with gold trapped behind the riffle bars. At 8:00 gold flecks are recovered from the Long Tom via a pan. At 8:30, a series of riffle boxes are placed together to form a sluice box -- the best of all placer mining tools.
Placer mining is the mining of stream bed (alluvial) deposits for minerals. This may be done by open-pit (also called open-cast mining) or by various surface excavating equipment or tunnelling equipment.
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 typically only a minuscule portion of the total deposit. Since gems and heavy metals like gold are considerably more dense than sand, they tend to accumulate at the base of placer deposits.
It is important to note that placer deposits can be as young as a few years old, such as the Canadian Queen Charlotte beach gold placer deposits, or billions of years old like the Elliott Lake uranium paleoplacer within the Huronian Supergroup in Canada.
The containing material in an alluvial placer mine may be too loose to safely mine by tunnelling, though it is possible where the ground is permanently frozen. Where water under pressure is available, it may be used to mine, move, and separate the precious material from the deposit, a method known as hydraulic mining, hydraulic sluicing or hydraulicking.
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This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD, 2k and 4k. For more information visit http://www.PeriscopeFilm.com