Editing Placer mining (section)

===Panning===
{{Main|Gold panning}}

[[File:Placer gold-mining, Korea, c1900.jpg|thumb|Panning for gold in [[Korea]], c. 1900]]
The simplest technique to extract gold from placer ore is [[Gold panning|panning]]. This technique has been dated back to at least the Roman Empire.<ref>{{Cite book|title=Roman Deep Vein Mining|last=Cohen Duncan|first=Lynn|year=1999}}</ref> In panning, some mined ore is placed in a large metal or plastic pan, combined with a generous amount of [[water]], and agitated so that the gold particles, being of higher [[density]] than the other material, settle to the bottom of the pan.  The lighter [[gangue]] material such as sand, mud and gravel are then washed over the side of the pan, leaving the gold behind.  Once a placer deposit is located by gold panning, the miner usually shifts to equipment that can treat volumes of sand and gravel more quickly and efficiently. Gold panning was commonly used on its own during the [[California Gold Rush|California gold rush]];<ref>{{Cite book|title=Western Mining|url=https://archive.org/details/westernmininginf0000youn|url-access=registration|last=Young|first=Otis|publisher=University of Oklahoma Press|year=1970|location=Oklahoma|pages=[https://archive.org/details/westernmininginf0000youn/page/108 108]–110|isbn=9780806109091 }}</ref> however, it is rarely profitable anymore since even an expert gold prospector can only process approximately one cubic yard of material for every 10 hours of work.<ref name=":0">{{Cite book|title=Methods of Placer Mining|last=Basque|first=G.|publisher=Heritage House|year=1999|location=Surrey, B.C.}}</ref>