Editing Placer mining (section)

===Underground mining===
[[File:Mining with steam points.jpg|thumb|Miners using jets of steam to melt the [[permafrost]] in an underground gold mine]]

In areas where the ground is [[permafrost|permanently frozen]], such as in Siberia, Alaska, and the Yukon, placer deposits may be mined underground.<ref name="Colliery Underground">{{cite book|title=Placer Mining: A Hand-Book for Klondike and Other Miners and Prospectors|year=1897|publisher=Colliery Engineering Co.|location=Scranton, Pa.|pages=[https://archive.org/details/placermininghand00coll/page/66 66]–69|url=https://archive.org/details/placermininghand00coll}}</ref> As the frozen ground is otherwise too hard and firm to mine by hand, historically fires were built so as to thaw the ground before digging it.<ref name="Colliery Underground" /> Later methods involve blasting jets of steam ("points") into the frozen deposits.

[[Placer mining#Deep leads|'''Deep leads''']] are accessed by techniques similar to conventional underground mining.