There are three principal methods of gold mining in California. Placer mining was one of the most popular, and involved removing gold from deposits in the ground, where it washed down from larger deposits. A faster, and much more destructive method was hydraulic mining, where gold was forcibly removed from deposits by spraying deposits with high volume, high pressure nozzles, washing entire hillsides down to a sluicing operation where heaver elements, like gold, could be separated out. The third mining method is hard rock ore mining where ore is extracted from mine shafts or open pit operations. The ore undergoes treatment that extracts gold salts from the ore, then goes through a smelting process to re-constitute the gold.