Copper

specimen number:
8311551

location:
Ridge Mine, Ontonagon Co., Michigan, USA

description:

A large sort of curving crystal of native copper. In great condition. This appears to have formed a cast after a previous unknown mineral.

The Ridge mine, situated near Mass City in Ontonagon County within the historic Evergreen range copper district of Michigan, United States, was a notable mid-nineteenth-century underground operation renowned for its early production of mass native copper. Geologically, this stratiform deposit is hosted within the Mesoproterozoic-age Portage Lake Volcanics of the Midcontinent Rift System, where mineralizing hydrothermal fluids filled the porous, brecciated amygdaloidal top of a specific basaltic lava flow known as the Evergreen Lode, precipitating pure native copper and native silver alongside secondary quartz, epidote, calcite, and prehnite. Historically, the property showed evidence of prehistoric exploitation by ancient Native Americans, who left behind numerous stone hammers in shallow pits along the outcropping vein. Modern industrial development began in 1850 when the Ridge Mining Company was formally organized, with miners quickly erecting an aggregate stamp mill and sinking three primary shafts that yielded profitable quantities of heavy barrel and mass copper through the 1850s and 1860s. The property was leased to independent tributor miners during subsequent economic downturns until 1899, when it was consolidated alongside the nearby Mass, Ogima, and Hazard mines into the Mass Consolidated Mining Company, which modernized the operations and continued underground extraction until escalating costs and post-World War I market stagnation forced a permanent closure of the interconnected complex in 1919.

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