A technique used in the nineteenth century in which miners would use a strong blast of water through a large hose to strip away soil, rock, and other material from an area to bare a vein of gold or silver.
An effective but destructive method of mining. Water under pressure was directed at hillsides of soft gravels through a hose with a nozzle called a monitor or giant, causing mud to run down into long lines of sluice boxes and causing banks to disintegrate. The incoming water often ran for many miles from the higher mountains in flumes that were costly to build, but water reached the mining site with enough force to shoot 400 feet into the air after it was dropped from hundreds of feet almost vertically down to the mining site. The by-product of hydraulic mining, thick mud and silt called slickens, ruined farm land downstream and caused navigation hazards in major rivers and San Francisco Bay, which led to its prohibition.