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rarely observed in lithologies of this area, but has been observed along faults and fractures in the <br />hornblende gneisses and amphibolites (D. Bove, written commun., 2003). Although rare, it is also reported <br />in late supergene veinlets that cut vein ores not far from the ground surface, and in late-stage hypogene <br />veinlets and vugs (Lovering, 1938). <br />Sampling Locations <br />in the summers of 2001 and 2002, 13 mine-waste composite samples were collected from a <br />variety of historical mine-wastes located in and around the Montezuma mining district in Colorado. Many <br />of these mine-wastes are identified in Wilson and LaRock (1992) and Munroe (2000). Locations of mine- <br />wastes sampled for this study are identified in figure 1. Specific information about each site-including the <br />mine name, drainage basin in which the mine-wastes are located, and the host rock in which the mines <br />reside-is given in table 1. <br />Table 1. Mine-wastes sampled, their location, and host-rock formation. <br />Figure 1. Location map for 13 mine dumps sampled for this study. <br />Sample Media <br />For this study, focus was applied to the leachate geochemical profile of the outer "skin" or upper <br />15 cm of the surface of the mine-waste pile. It is important to characterize the geochemical potential of the <br />outer skin of mine-waste piles because the skin of a mine-waste pile is very geochemically reactive. This <br />reactivity is due to contact with the atmosphere. In the case of these historical mine-waste piles, the outer <br />surface of the piles have been exposed to atmospheric oxygen and severe weathering for extended periods <br />of time. Weathering processes include wide temperature fluctuations, innumerable freeze/thaw cycles, high <br />winds, solar influences, biologic activity, and precipitation in all forms. As a result of these factors, wet/dry <br />cycles cause repeated leaching, that, in turn, produce continuous wicking, rinsing, and reformation of <br />soluble mineral salts and other secondary minerals. At the same time, the body of the pile acts as a huge <br />sulfide reservoir, providing acid and metals to replenish material leached from the surface. <br />Sample Collection <br />Mine-wastes were sampled using a composite sampling technique (Smith and others, 2000). The <br />sampling procedure consisted of collecting at least 30 random samples from a mine-waste pile using a steel <br />trowel and a plastic bucket. Coarse material (material that was larger than the top knuckle of the thumb) <br />was discarded during collection. All increments were put into a 5-gallon plastic bucket and mixed. If the <br />sample was wet, it was first air-dried on a plastic tarp and then mixed. The mine-waste composite was then <br />sieved to pass a 2-mm stainless steel screen. The <2-mm fraction was saved for leaching and further <br />analysis, and all material >2 mm was discarded. <br />Hageman_SIR_2508.doc <br />4 <br />7/21/2004 2:50 PM