Copper from Keweenaw County, Michigan, USA - image 1
Copper from Keweenaw County, Michigan, USA - image 2

Copper from Keweenaw County, Michigan, USA

$2,400.00

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An aesthetic branching grouping of sharply formed native copper crystals. Complete all around, this is in super condition. By Michigan classic. Copper mining in Keweenaw County, Michigan, represents a major historical component of the Lake Superior native copper district, characterized by the extraction of elemental copper rather than sulfide ores. Geologically, the deposits are hosted within the Mesoproterozoic Portage Lake Volcanics, a thick sequence of basaltic lava flows interbedded with conglomerate rocks that filled the Midcontinent Rift system. Hydrothermal fluids migrating through the rift basin deposited native copper and silver within the porous, vesicular tops of the basalt flows (amygdaloids) and the matrices of the conglomerates, often associated with minerals like calcite, epidote, and pumpellyite. Industrial mining in the county commenced in 1944 with the opening of the Cliff mine, which proved the economic viability of the district's massive fissure veins. This discovery triggered a major mining boom, leading to the development of major underground operations by companies such as the Central Mining Company, Allouez Mining Company, and the Ahmeek Mining Company. Commercial extraction peaked during the late nineteenth and early twentieth centuries, but steadily declined due to depletion and deep operational costs, with primary production in the county drawing to a close by the late 1960s when Calumet and Hecla permanently ceased its regional operations.

Product details

SpeciesCopper
SizeSmall Cabinet
Dimensions10.0 x 5.5 x 1.0 cm
Listed on07/16/2026
LocalityUSA, Michigan, Keweenaw County
SKU9273165
Current owner
WM
Weinrich MineralsFeatured
3,406 for sale·9 sold

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Copper
Mineral guide
Learn about Copper
native copper with spinel-twinned crystals and arborescences; notable from Lake Superior, Itauz, Dongchuan, Corocoro, prized for color and localities.
Copper
Regional guide
Copper from Keweenaw County
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Locality guide
Keweenaw County
Keweenaw County, USA - native copper and silver from the Lake Superior district, with sculptural copper crystals and mineral associations for collectors.