Prehnite with Copper

specimen number:
2062243

location:
Silver Pit, Copper Falls, Keweenaw Co., Michigan

description:
Sparkling attractive green crystallized prehnite across the front of matrix with small crystals of native copper. In great condition. Quite choice for the species from this area. Collected in 1999. Datolite is present as well.

The Silver Pit, situated within the historic Copper Falls mine property near Eagle Harbor in Keweenaw County, Michigan, was a highly specialized underground extraction site famous for its unusual concentration of precious metal. Geologically, this specific working targeted a localized, hydrothermally mineralized fissure vein that cut vertically through the amygdaloidal basalt flows and conglomerates of the Mesoproterozoic Portage Lake Volcanics. While the surrounding district was characterized almost exclusively by native copper, the hydrothermal fluids in this distinct structural conduit precipitated significant quantities of native silver alongside copper, calcite, and datolite within open fractures and brecciated zones. Historically, the broader Copper Falls property was first explored in 1845, with the lucrative Silver Pit working specifically developed and mined during the peak operational years of the Copper Falls Mining Company between 1850 and 1893. The pit itself was worked intermittently to extract rich pocket deposits of silver before corporate consolidations and the eventual depletion of the narrow fissure vein led to the permanent abandonment of the site in 1893 when the main Copper Falls operations closed.

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