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Dames & Moore, 1999 - USDA Forest Service

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6.10 CONCLUSIONS<br />

Based on the results of the fate and transport analysis in conjunction with the current conceptual site<br />

model, conclusions are listed below; specific conclusions have also been presented in each main<br />

subsection of Section 6:<br />

The primary sulfide minerals in the Holden Mine ore deposit include pyrite, pyrrhotite,<br />

sphalerite and chalcopyrite.<br />

0 The Holden Mine deposit is hosted by the Buckskin Schist, which is a q ua amphibole<br />

schist sequence with at least two horizons of intermittent marble beds and calcareous<br />

schists. The dominant silicates are plagioclase and biotite (aluminum-based).<br />

Host rock mineralogy is the primary factor affecting water chemistry at the Site.<br />

Weathering of these minerals, ,especiall~ sulfide minerals, dominates Site water<br />

chemistry. Non-sulfide mineralogy of the tailings is expected to be dominated by<br />

minerals contained in the ore and in diabase dikes whereas the mine wall rocks are<br />

dominated by biotite schist.<br />

Secondary mineralization and precipitates produced by weathering processes are visibly<br />

evident throughout the Site, including orange brown iron stains (iron oxyhydroxides) on<br />

waste rock and tailings, white precipitates (amorphous aluminum hydroxide) in the 1500-<br />

level main portal drainage, green stain (copper carbonate) on marble waste rock in the<br />

waste rock piles, and efflorescent crusts (metal sulfates) in the mill building and where<br />

seepage emerges along the toes of the tailings piles.<br />

. .,.<br />

a<br />

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