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AN EVALUATION OF THE ACID GENERATING POTENTIAL <br />IN WALL ROCK AND ORE MATERIALS OF THE <br />GOLD HILL DISTRICT, BOULDER COUNTY, COLORADO <br />By: Harold W. Miller, B.Sc., M.Sc. <br />Overview <br />The Boulder County telluride belt is located at the northeastern end of the Colorado <br />mineral belt. Although the Boulder County telluride deposits are widely scattered over a <br />broad north-trending belt, most of the production has come from a few highly <br />concentrated centers that exhibit strong structural control. The tazgest and most <br />productive precious metal mining district in the Boulder County telluride belt is the Gold <br />Hill mining district. One of the most productive centers of mineralization in this district <br />is located neaz the town of Gold Hill, within an area of about four square miles. This area <br />has produced more gold and silver than any other area of similar size in the district or the <br />telluride belt, and includes the important Slide, Prussian, Cold Spring, Red Cloud, <br />Alamakee, Gold Ring, Horsfal, Cash, Who Do, St. Joe, Black Cloud, Rex, and Victoria <br />mines. <br />The Boulder County telluride belt is part of a broad, north-trending azea of precious metal <br />mineralization encompassing about 40 square miles. Precambrian granites, gneisses, and <br />schists are the predominant country rocks. These rocks have been intruded by Early <br />Tertiary stocks and dikes which have a close genetic relationship to the gold and silver <br />ores. A strong system of northwest trending faults, or breccia reefs, cut the telluride belt <br />and exerted a significant influence on the distribution of the ore mineralization. <br />Most of the productive veins fill steeply dipping, northeast trending fault fissures that can <br />be traced on the surface for more than half a mile and aze from 1 to 5 feet wide. While <br />the gold-silver telluride veins have accounted for most of the production from the <br />