Productive historic mines in 13 mining districts, of many geochemical types, were investigated in May of 1998. Reconnaissance field observations were made and samples of mine dumps, mine drainage waters, and mill tailings have been collected to characterize the geochemical signature of these materials and to determine their actual or potential contamination of surface or ground waters. Field observations suggest that visible indicators of acidic mine drainage are rare, and field measurements of pH and chemical analyses of several kinds of materials indicate that only a few sites release acid or significant concentrations of metals.
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USGS Numbered Series
Hydrogeochemical investigations of some historic mining areas in the western Humboldt River basin, Nevada