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Aeolian placers are valuable minerals found in arid regions freed from their source rock by wind actions. Wind erosion leaves a cement like substance in which material like gold are found. Wind action blows sand and dirt away leaving the deposits close to the surface. Historically, aeolian placers
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Beach placers are formed in sand and gravel deposited along the edge of large bodies of water and are typically found where streams or rivers flow into a large body of water. Materials collect as beach placers by continuous wave action and currents. Some important examples of beach placers include
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allows placer minerals to resist mechanical breakdown and loss of mass from abrasion during transport. A hardness greater than quartz is desired, however substances such as gold typically deform and create irregularly shaped nuggets when subject to mechanical stress.
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are found in varying amounts. Some of the most productive beach placers are considered ancient beaches that are now far inland from the water, these placers no longer shift with storms and tidal action but with wind and rainfall.
197:. Early mining operations were probably a result of placer deposits as they were easily accessible and potential size. The events known as gold/diamond rushes were caused by placer deposits and have proved to be plentiful.
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Paleo-placer deposits are deposits of minerals from all of the above placer types that occurred millions of years ago. These deposits are typically very far underground in ancient riverbeds, beaches, or slopes. The
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Basin, South Africa is the largest gold deposit in the world and is considered a paleo-placer, it has produced over 1.5 billion ounces of gold. The
Witwatersrand Basin is considered an ancient alluvial placer.
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Alluvial placers are those formed in river or stream sediments. Another name for alluvial placers are stream placers. Typical locations for alluvial gold placer deposits are on the inside bends of
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Eluvial placers are deposits of metal formed on hillsides and slopes weathered by rainfall and wind. Lighter materials are carried away and weathered leaving concentrations of valuable metals.
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Gold bearing beach placers consist of large strips of black sands and are typically constantly changing as a result of storms or sporadic wave action. Typically beach placers are populated by
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material, which is able to be transported away from the trap site. Only if the deposit is winnowed in this way can the minerals be concentrated to economic levels.
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Alluvial placers are formed by the deposition of dense particles at a site where water velocity remains below that required to transport them further.
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is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the
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or other barrier. Stream placers are the most economical and common types of placers and have provided many with riches in the past.
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429:, Western United states, where the climate is arid and the ground is relatively level leaving wind as the primary erosion force.
226:.The weathering process allows for the accumulation of placer minerals, while less dense material such as quartz are swept away.
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processes (transported by water) to a source that becomes a diamond deposit. Alluvial diamond deposits are mined after removing
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have been mined by hand with simple tools by miners due to the proximity to the surface, and small concentration.
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from the top of the rich, diamond-gravel layer. Roughly 10 percent of diamonds are mined from alluvial diamond
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form at high temperatures and pressures. These diamonds are then weathered from the source and swept away by
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253:, Minerals lacking chemical stability will form less desirable alteration when subject to chemical breakdown.
762:"Mineral, chemical and radiological investigation of a black sand at Touzla Cape, near Thessaloniki, Greece"
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This article is about the term used in mining and geology. For the geographical and nautical term, see
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Eluvial placers are typically not large enough to support large scale mining, however in one case in
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processes. To accumulate in placers, mineral particles must have a specific gravity above 2.58.
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Density sorting of heavy minerals during sediment transport forming placers between ripple marks
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above 2.58. The separation of the valuable minerals from the most common non-economic mineral,
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To form a placer deposit, the particles desired must show a marked density contrast with the
887:"What is Eolian Placer Gold? - Gold Prospecting Mining Equipment Detectors Snake Protection"
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are a major source of diamonds. Kimberlites are long "pipes" of lava brought up from the
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374:, zircon sands in Brazil and Australia as well as diamond marine gravel in South Africa.
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there has been large scale gold mining operations based on placer deposits at
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943:"Where Does Placer Gold Come From? – Part 3 Placer | West Coast Placer"
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is important for a placer mineral to resist chemical breakdown such as
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in Africa mentioned above is a recognized alluvial diamond deposit.
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Accumulation of valuable minerals formed by gravity separation
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Substances commercially mined from placer deposits include:
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Placer materials must be both dense and resistant to
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147:, beach placers, aeolian placers and paleo-placers.
323:Beach placer deposit of heavy minerals (dark) in a
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760:Filippidis, Anestis; Clouvas, Alexander (1997).
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370:black sands of Oregon, gold deposits in
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210:Placer minerals are defined as having a
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39:This article includes a list of general
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675:"Placer formation and placer minerals"
157:Placer environments typically contain
766:Environmental Geochemistry and Health
963:"Alluvial Diamond Mining Fact Sheet"
701:– via Elsevier Science Direct.
673:Els, Gerhard; Eriksson, Pat (2006).
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916:Mineral Processing & Metallurgy
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139:. Types of placer deposits include
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477:containing high concentrations of
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201:Characteristics of placer minerals
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699:10.1016/j.oregeorev.2005.02.001
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425:Aeolian placers are common in
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910:Michaud, David (2016-10-23).
711:: CS1 maint: date and year (
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891:www.goldrushtradingpost.com
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863:"Placer deposit | geology"
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131:is an important source of
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788:– via SpringerLink.
165:with variable amounts of
544:Precambrian paleoplacers
867:Encyclopedia Britannica
807:Encyclopedia Britannica
778:10.1023/A:1018498404922
738:Encyclopedia Britannica
60:more precise citations.
840:Western Mining History
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282:placer deposit at the
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970:World Diamond Council
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772:(2). et al: 83–88.
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679:Ore Geology Reviews
593:Witwatersrand Basin
551:, from the mineral
511:, from the mineral
492:, from the mineral
490:Rare earth elements
912:"Types of Placers"
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247:Chemical stability
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351:paleoplacer
278:Section of
195:cassiterite
123:, meaning "
58:introducing
996:Categories
948:2021-04-06
921:2021-03-26
896:2021-03-25
872:2021-03-25
845:2021-03-25
812:2021-04-06
743:2021-02-11
647:References
626:Black sand
585:overburden
353:deposits (
300:escarpment
191:wolframite
159:black sand
152:weathering
41:references
975:August 4,
786:126447895
549:Zirconium
479:magnetite
475:ironsands
427:Australia
383:magnetite
304:waterfall
251:oxidation
242:Stability
163:magnetite
599:See also
591:. The
581:alluvial
577:diamonds
564:Diamonds
531:ilmenite
527:Titanium
513:monazite
504:Sapphire
494:monazite
456:Diamonds
391:chromite
387:platinum
379:ilmenite
347:alluvial
334:, India)
286:, Alaska
280:alluvial
235:Hardness
230:Hardness
187:chromite
175:monazite
171:hematite
167:ilmenite
141:alluvium
125:alluvial
687:Bibcode
542:, from
540:Uranium
509:Thorium
473:, from
332:Chennai
224:density
206:Density
145:eluvium
127:sand".
117:Spanish
105:geology
54:improve
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575:where
573:mantle
553:zircon
535:rutile
486:metals
466:Garnet
407:Nevada
325:quartz
314:gangue
296:creeks
292:rivers
216:quartz
193:, and
183:zircon
179:rutile
121:placer
113:placer
43:, but
966:(PDF)
782:S2CID
119:word
977:2019
713:link
533:and
499:Ruby
471:Iron
461:Gold
389:and
381:and
355:USGS
349:and
328:sand
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518:Tin
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