Copper

specimen number:
2062277

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

description:
Very large crude crystal grouping of copper coming off matrix. Collected approximately in 1950. In good condition all around.

The Allouez mine, located near Bumbletown in Keweenaw County, Michigan, was a major underground native copper operation targeting the Allouez conglomerate bed and later the Kearsarge amygdaloid lode. Geologically, the deposit is hosted within the Portage Lake Volcanics, a thick sequence of Precambrian basalt flows and interbedded sedimentary layers where ascending hydrothermal fluids deposited pure elemental copper alongside calcite, quartz, and epidote within rock pores and fractures. The Allouez Mining Company was organized in 1859 and began sinking its first shafts in 1869, officially starting commercial production in 1874. The operation faced initial financial difficulties due to the erratic nature of the conglomerate mineralization, but performance improved significantly when a new company reorganized the site in 1903 to sink the No. 1 and No. 2 shafts into the richer Kearsarge lode. Absorbed by the Calumet and Hecla Consolidated Copper Company in 1923, the mine produced over one hundred million pounds of refined copper before falling ore grades and adverse economic conditions forced the permanent cessation of all underground mining at the property in 1932.

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