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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 ...
A cluster of deposits is in the main part of the Yentna district, near the Dutch Hills. The productive deposits here have been placer gold deposits with byproduct platinum and locally abundant cassiterite. Gold-bearing lodes in the Yentna district, which have not been as well described, include small and locally very rich deposits associated ...
"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.
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 ...
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.
However, the richest deposits for the region, and indeed the world, lie in Southeastern Asia, stretching from Yunnan in China to the Malay Peninsula. The deposits in Yunnan were not mined until around 700 BC, but by the Han dynasty had become the main source of tin in China according to historical texts of the Han, Jin, Tang, and Song dynasties ...
These so-called placer deposits are often beach or fossil beach sands and contain other heavy minerals of commercial interest such as zircon and ilmenite. Monazite can be isolated as a nearly pure concentrate by the use of gravity, magnetic, and electrostatic separation. Monazite sand deposits are prevalently of the monazite- composition.
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