Placer mining

In 1986, domestic consumption of copper in the United States was 2.14 million metric tons, and mine production was 1.14 million metric tons, mostly from mines in Arizona, New Mexico, and Michigan. The major copper deposits in the United States are of hydrothermal origin and are uniformly distributed in fractures or veins (ATSDR 1990). Copper is the major toxic component in streams impacted by active placer mines (Buhl and Hamilton 1990). About 60% of copper metal is eventually recycled in 1986, smelting of scrap copper produced an additional 0.9 million metric tons of copper. Also in 1986, 1.1 million tons of copper were imported into the United States, mostly from Canada, Chile, Peru, and Mexico (ATSDR 1990). 

Buhl, K.J. and S.J. Hamilton. 1990. Comparative toxicity of inorganic contaminants released by placer mining to early life stages of salmonids. Ecotoxicol. Environ. Safety 20 325-342. 

This east-west difference reflects dominance in sediment source in the eastern valley by material derived from glacial debris and placer mining, and the presence of ultramafic rocks in the headwaters of western streams and ultramafic constituents in sediments on the west side of the valley. 

Aquatic or marine mining is the removal of unconsoUdated minerals that are near or under water, with processes in which the extracted mineral is moved by or processed in the associated water. This type of mining may also be referred to as alluvial mining or placer mining. The two major types of aquatic or marine mining are dredging and hydraulicking. 

Revolving screen Inclined trommel, scrubber, or barrel cylindrical, rotating wire cloth, and perforated plate 15-20 rpm open at ends Scrub, wash, rough size placer mining low capacity and efficiency... 

A number of tests are recommended to determine the dredgeability of soils and their behavior in placer mining or slurry mixing (Table 1-7). In nature, silts may be found in association with clays thus, the parameters for both silts and clays should be assessed. The following testing parameters are accepted by the industry. 

TABLE 1-7 Testing Parameters on Soils to Determine DredgeabUity, Suitability for Placer Mining, or Slurry Preparation... 

Wilson, W. K., Jr. (1948). The problem of permafrost. The Military Engineer, 40,162-164. Wimmler, N. L. (1927). Placer-mining methods and costs in Alaska U.S. Bureau of Mines Bulletin... 

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