Industrial placer gold mining is a messy business. National Park Service Natural Resource Report:Ī history of NPS clean-up efforts at the historic Coal Creek Mining District This early success convinced McRae and Patty to invest in a second, nearly identical dredge which they constructed just five miles to the west in the Woodchopper Creek drainage. In its first two weeks of operation the dredge brought in between sixty cents and one dollar per cubic yard of gravel and yielded $27,000 in gold. By applying heat, the mercury can be removed to be used again and the gold can be melted into bars. Using a technique that dates back hundreds of years, the dredge operators laced their sluice boxes with mercury which chemically bonds with gold and allows the tiniest particles of gold to be scooped up in a blob called an amalgam.
To do this the dredge functioned like an enormous washing machine which pulled in thousands of cubic yards of gravel with its 62-unit bucketline, tumbled and sprayed the material to segregate large rocks from finer material, and used a system of sluice boxes to allow bits of gold to be captured while the waste rock was discarded out the back. The theory behind gold dredging is the same as any placer mining operation: separate sand and gravel from gold.
The Coal Creek dredge stacker and tailing piles.
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