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The Vindicator Mine (Figure 6) is in a small tributary to the upper portion of Basin Creek in the Beaverhead-Deerlodge National Forest (Township 7 North, Range 6 West, Section 12). The site (Figure 7) was inventoried and sampled in June 1992 and summarized in a report on the Basin Creek drainage (Metesh and others 1994).
|Figure 6-The workings of the Vindicator Mine in southwestern Montana are shallow and lie within a narrow shear zone. The|
seeps and adit discharges are fed by surface water flowing into the drainage.
The mine exploited near-surface veins contained within three parallel shear zones that were an average of 5 feet wide. Gold and silver were the target ores, but quartz, calcite, pyrite, galena, sphalerite, tetrahedrite, chalcopyrite, and tourmaline are present in the veins. The total production of the mine, which operated from 1936 to 1940, was about 92 tons. The total extent of workings is less than 1,000 feet. No maps are available for the underground workings. Based on the location of the adits and associated waste-rock dumps, few or none of the workings are perpendicular to the shear zone. The workings are probably shallow and restricted to a narrow zone coincident with the natural drainage.
|Figure7-The sides of this manmade channel at the Vindicator Mine in southwestern Montana are prone to|
collapse, adding sediment to the stream.
Discharge from adits (Figure 8) and seeps ranged from less than 0.5 gallons per minute at the upper part of the site to about 12 gallons per minute at the lowest adit. Staining and vegetation at the site indicate that the rate of discharge from the springs and adits varies seasonally. The water from the site was generally poor quality. Although the pH was nearly neutral, drinking water criteria and aquatic life criteria were exceeded for dissolved cadmium, copper, lead, aluminum, and zinc at two of the larger seeps.
Adit discharges at the Vindicator mine could be reduced or eliminated by reducing the recharge to the workings. With shallow workings restricted to a narrow zone within the bottom of the ephemeral drainage, the recharge to the workings is probably dominated by water infiltrating from surface runoff. Surface application of low permeability material over the top of the regraded waste-rock dumps and excavations would reduce the infiltration of water into the workings. The result should be reduced or eliminated flow from the adits and seeps associated with the mine.
|Figure 8-A closed adit at the Vindicator Mine.|
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