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Abstract

The Ironclad/Globe Hill mine consists of two different gold deposits that were mined together by open pit techniques and are currently being backfilled. The Ironclad ore body was a mineralized breccia pipe while the Globe Hill deposit was dominated by irregular-shaped orebodies at structural intersections adjacent to an unmineralized breccia pipe.

The Ironclad/Globe Hill deposits were first mined by several small underground operations in the early 1890's and since the gold was free milling, it was processed using a small but efficient vat leach system. Open pit mining began in 1917 and continued sporadically until 1994. Attempts were made during World War One to mine a large body of manganese ore but proved unsuccessful. Tonnages and grade of the area are unknown for the earlier operations, but from June of 1991 to May of 1994 4.8 million tons of 0.039 opt SL with an average recovery of 76 percent were mined from both deposits using open pit techniques.

The dominant geologic features of the deposits are the two unconsolidated breccia pipes along a major N30W-trending structure just north of the "Granite Island" (Figure 1). The Globe Hill breccia is a roughly triangular-shaped (1000 feet on a side) while the Ironclad breccia (500 feet by 300 feet) is controlled by northeast- and northwest-trending structures. Both breccias are generally matrix-supported, monolithic (same lithology as the host rock) and incompetent.

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