HYDRAULIC MINING

use of a powerful jet of water to dislodge minerals present in unconsolidated ground. In the hydraulic mining of gold, the rebounding stream of water and mineral fragments is directed into sluices in which the gold settles behind baffles but the lighter waste matter is washed away. In hydraulic mining of coal, the water simply breaks the coal from the seam and washes it to a collecting point. See also placer mining.