Noun
hydraulic mining (uncountable)
A form of mining that uses pressurized water jets to dislodge rock or move sediment.
In the 1860s and continuing into the early 20th century, miners dumped staggering quantities of mud and gravel from hydraulic mining operations into the upper Sacramento and San Joaquin Rivers. Source: Internet
Starr, Kevin (2005), p. 89. In a modern style of hydraulic mining first developed in California, and later used around the world, a high-pressure hose directed a powerful stream or jet of water at gold-bearing gravel beds. Source: Internet