A gol nugget is a naturally occurring piece of native gold. Watercourses often concentrate the nuggets and they are recovered by placer mining, but they may also be found in residual deposits where the gold-bearing veins or lodes have decayed. Nuggets are also found in the tailing piles of previous mining operations, especially those left by gold mining dredges. They are never pure 24K in composition but rather about 20 to 22K (~about 83% to 92%). Nuggets are also referred to by their "fineness", for example "865 fine" means the nugget is 865 parts per thousand in gold. The common impurities are silver and copper.