Rhodochrosite

specimen number:
2133375

location:
Sunnyside Mine, San Juan Co., Colorado, USA

description:
Nice thumbnail for this classic Colorado locality. A cluster of pink rhombohedral rhodochrosite crystal. In good condition all around.

The Sunnyside mine, located near Silverton in the Eureka mining district of San Juan County, Colorado, was a major underground base and precious metal operation. Geologically, the deposit is situated within the silver-rich San Juan volcanic field, where mineralization was structurally controlled by the intersecting faults and ring-fracture zones of the Miocene-aged Silverton caldera. Hydrothermal fluids circulating through these fractures deposited vast vein systems rich in gold, silver, galena, sphalerite, and chalcopyrite, hosted within a gangue dominated by quartz and rhodochrosite. Gold was first discovered at the site in 1873, and the property was developed heavily under the leadership of John Terry in the 1890s, becoming one of the most prominent producers in the region. The mine operated with various periods of modification and ownership changes throughout the twentieth century, including a major production era managed by the Standard Metals Corporation from 1959 until a catastrophic lake-tapping flood temporarily halted operations in 1978. Underground extraction resumed afterward but permanently ceased in 1991 due to low metal prices and environmental liabilities, concluding more than a century of industrial activity at the site.

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