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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]
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 ...
Sedimentary placer deposits are known as 'leads' or 'deep leads'. Placer deposits are often worked by fossicking, and panning for gold is a popular pastime. Laterite gold deposits are formed from pre-existing gold deposits (including some placer deposits) during prolonged weathering of the bedrock. Gold is deposited within iron oxides in the ...
Newly discovered deposits like Confederate Gulch attracted young footloose men, motivated by a desire to get rich quickly. [9] Towns that sprang up at placer gold strikes were jerry built, ephemeral and hectic places and Diamond City and the other Confederate Gulch communities were no exception. [9] As long as gold was produced they boomed along.
"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.
For example; the medium-sized Coburn mineral sands deposit, Western Australia, is 230 million tonnes at 1.1% heavy minerals, and is 13 km long. The Tormin mine, on the Western Cape of South Africa's coastline, provides a unique ocean beach feature, which exposes the resource to wave and tidal conditions that result in a natural jigging effect.
The word placer derives from the Spanish placer, meaning shoal or alluvial/sand deposit, from plassa (place) from Medieval Latin placea (place) the origin word for "place" and "plaza" in English. The word in Spanish is thus derived from placea and refers directly to an alluvial or glacial deposit of sand or gravel.
Recreational mining is typically small-scale placer mining but has been challenged for environmental reasons. The disruption of historic gold placer deposits poses risks of reintroducing pollutants from past mining activities , such as mercury remaining in mine deposits and tailings .