Hydraulic mining was used widely in the Californian gold rush, and involved breaking down alluvial deposits writy of commercial gold recovery operations since the middle of the 20th century where open pit and or sub-surface mining techniques are used.
Hydraulic mining was used widely in the Californian gold rush, and involved breaking down alluvial deposits with high-pressure jets of water. Hard rock ores have formed the basis of the majority of commercial gold recovery operations since the middle of the 20th century where open pit and or sub-surface mining techniques are used.