Accumulation of valuable minerals formed by gravity separation
This article is about the term used in mining and geology. For the geographical and nautical term, see Placer (geography).
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Heavy minerals (black) forming placers along ripple marks.
In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes.[1] 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 materials must be both dense and resistant to weathering processes. To accumulate in placers, mineral particles must have a specific gravity above 2.58.[1]
Placer environments typically contain black sand, a conspicuous shiny black mixture of iron oxides, mostly magnetite with variable amounts of ilmenite and hematite.[3] Valuable mineral components often occurring with black sands are monazite, rutile, zircon, chromite, wolframite, and cassiterite.[3] Early mining operations were probably a result of placer deposits as they were easily accessible and potential size.[4] The events known as gold/diamond rushes were caused by placer deposits and have proved to be plentiful.[4]
^ abEls, Gerhard; Eriksson, Pat (2006). "Placer formation and placer minerals". Ore Geology Reviews. 28 (4): 373–375. Bibcode:2006OGRv...28..373E. doi:10.1016/j.oregeorev.2005.02.001 – via Elsevier Science Direct.{{cite journal}}: CS1 maint: date and year (link)
^ abFilippidis, Anestis; Clouvas, Alexander (1997). "Mineral, chemical and radiological investigation of a black sand at Touzla Cape, near Thessaloniki, Greece". Environmental Geochemistry and Health. 19 (2). et al: 83–88. doi:10.1023/A:1018498404922. S2CID 126447895 – via SpringerLink.
California Gold Rush. Types of placerdeposits include alluvium, eluvium, beach placers, aeolian placers and paleo-placers. Placer materials must be both dense...
total deposit. Since gems and heavy metals like gold are considerably denser than sand, they tend to accumulate at the base of placerdeposits. Placer deposits...
minerals, tin (Sn), tungsten (W), and rare-earth elements (REEs). A placerdeposit is considered alluvial if formed via river, colluvial if by gravity...
fine sands containing minerals such as magnetite, found as part of a placerdeposit. Another type of black sand, found on beaches near a volcano, consists...
locations for placer gold. Sampling and assaying a placer gold deposit to determine its economic viability is subject to many pitfalls. Once placer gold is...
panning, or simply panning, is a form of placer mining and traditional mining that extracts gold from a placerdeposit using a pan. The process is one of the...
Look up placer in Wiktionary, the free dictionary. Placer may refer to one of the following: PlacerdepositPlacer sheep Placer mining Placer (geography)...
1989). "Sedimentological controls on gold in a late Pleistocene glacial placerdeposit, Cariboo Mining District, British Columbia, Canada". Sedimentary Geology...
lode gold, and 2.2 million troy ounces (68.4 tonnes) of placer gold. The rich placerdeposits of the Columbia Basin-Jamestown-Sonora district were found...
Deposit may refer to: Deposit (finance) (also security deposit) A down payment or partial payment in advance Deposit (town), New York Deposit (village)...
In an electoral system, a deposit is the sum of money that a candidate for an elected office, such as a seat in a legislature, is required to pay to an...
occasionally precious metals or gemstones. Heavy mineral sands are placerdeposits formed most usually in beach environments by concentration due to the...
quartz and other resistant minerals. Eluvial ore deposits are those such as tungsten and gold placerdeposits formed by settling and enriched by the winnowing...
in a placer claim is almost always gold, although other nations mine placerdeposits of platinum, tin, and diamonds. In the United States, a placer claim...
The Rock Flat Placer is a small placerdeposit in central Idaho which is part of the Meadows Mining District. It is known to produce gold, corundum, garnet...
Madre de Dios, located east the town of Máfil in Chile, is a placerdeposit of gold that has been mined several times since its discovery in 1556. The...
is often small-scale placer mining but has been challenged for environmental reasons. The disruption of old gold placerdeposits risks the reintroduction...
Legal deposit is a legal requirement that a person or group submit copies of their publications to a repository, usually a library. The number of copies...
from ore bodies, lodes, veins, seams, reefs, or placerdeposits. The exploitation of these deposits for raw materials is dependent on investment, labor...
Placer mines in the Zane Hills on Bear Creek, a tributary of the Hogatza River, are the biggest source of gold from the district. Placerdeposits clustered...
Creek, and Bullion mines of British Columbia, Canada and the Horokanai placerdeposit, of Kamikawa Subprefecture, Hokkaidō, Japan. Rutheniridosmine data on...
iron with a composition from Ni2Fe to Ni3Fe. Awaruite occurs in river placerdeposits derived from serpentinized peridotites and ophiolites. It also occurs...
Deposit insurance or deposit protection is a measure implemented in many countries to protect bank depositors, in full or in part, from losses caused by...
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