Copper

specimen number:
2242003

location:
Central Mine, Keweenaw Co., Michigan, USA

description:
Sharp lustrous crystals of native copper, these very large measuring to 3.5 cm in size, coming off matrix. In great condition.

The Central Mine, located on the Keweenaw Peninsula in Michigan, was one of the most successful and longest-lived operations in the Lake Superior Copper District. Geologically, the mine exploited a fissure vein deposit that cut across the regional basaltic lava flows and conglomerate beds of the Portage Lake Volcanics, where hydrothermal fluids deposited nearly pure native copper within the fault systems. Unlike many nearby mines that focused on amygdaloidal or conglomerate lodes, the Central Mine was famous for its massive native copper masses found within the "Central Vein." Historically, the mine was discovered in 1854 when prospectors found ancient mining pits, leading to the formal organization of the Central Mining Company. Industrial operations began in 1856 and continued with remarkable consistency, paying out dividends for over thirty years as the shaft reached depths exceeding 2,700 feet. While the most productive years occurred between 1860 and 1890, the mine eventually faced depletion of its high-grade masses and closed in 1898.

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