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Sampling for Gold in River Bars, Koskokwim River Basin, Alaska.
River bars were sampled over a 50-mile interval of the Kuskokwim River to determine the possibility of their containing significant amounts of gold. One-quarter cubic yard samples were concentrated by washing in a small, simple sluice box, and the concentrate further reduced by hand panning and then assayed. Colors of very fine gold were seen in the pan concentrates from all samples in the 50-mile interval, but assay results varied from nothing to about 2 cents per cubic yard of river bar material. It is questionable how much of the total amount of gold present in the samples was recovered in the concentrate; probably much less than 50 percent. The work indicated that the river bars contain free gold, and gold is presently being transported and deposited by the silt-laden waters. Additional investigation would be necessary to determine the extent and importance of this potential gold source; recovery in large-scale channel dredging operations, or as a byproduct in harbor excavations might be of economic significance.
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division