The Homestake Gold Mine

The Homestake Gold Mine is located in Lead, SD (fig 1). The Homestake Gold Mine was the largest gold mine in the western hemisphere, and it was the United States’ longest continuously operating mine until it closed in 2002. The mine closed because it was costing more to get the gold out than the gold was worth hence why mining is called economic geology. The Homestake was also the deepest mine in the western hemisphere. The Homestake gold mine has three main formations in it. The formations from oldest to youngest are the Poorman, the Homestake, and the Ellison. The gold is only found in the Homestake Formation (Caddey et al. 1991). The Poorman Formation is called the Poorman for a reason because if you were to mine the Poorman Formation you would go poor because there are no valuable minerals in the formation. The Poorman Formation is a sericite-biotite phyllite and averages 1,500m of thickness (Caddey et al. 1991). The Homestake Formation is a Gruerite-siderite schist and iron formation and can range from 1 to 125m thick (Caddey et al. 1991). The Homestake is 125m think in the fold hinges (Caddey et al. 1991) and hence why the folds contain the most gold (Rye and Rye 1974). The Ellison Formation is a sericite-biotite phyllite that has an average thickness of 400m …show more content…
1991). The Homestake formation is an iron and magnesium rich carbonate (Rye, Doe, and Delevaux 1974). The magnesium rich mineral is sideroplesite (magnesium sericite) (Norton 1971). There is also grunerite and cummingtonite found in the Homestake Formation (Morelli et al. 2010). The gold is hosted within a quartz veined sulfide rich segments of a carbonate iron formation, which are early Proterozoic in age (Caddey et al. 1991). The sulfide minerals that are associated with the gold are pyrrhotite, pyrite and arsenopyrite (Norton