Copper

specimen number:
2062220

location:
Laurium Mine, Houghton Co., Michigan, USA

description:
A large fairly well-formed crystal of copper 2.7 cm across embedded up on matrix. Collected in 1998. Minor epidote is present.

The Laurium mine, situated within the village of Laurium in Houghton County, Michigan, United States, was a historic underground copper operation that worked the highly mineralized Kearsarge amygdaloidal lode on the Keweenaw Peninsula. Geologically, this deposit is hosted within the Proterozoic-age Portage Lake Volcanics, where a thick sequence of vesicular basaltic lava flows underwent extensive structural tilting and faulting. Upward-migrating, hot, hydrothermal fluids carrying dissolved copper circulated through the porous, fragmental flow tops, precipitating fine grains and localized mass aggregates of native copper alongside secondary epidote, chlorite, and calcite within the rock cavities. Historically, the property was organized by the Laurium Mining Company in 1895, but active underground development did not begin in earnest until 1909 when a three-compartment inclined shaft was sunk to explore the potential extension of the rich copper lode. The operation expanded into a moderately sized industrial facility equipped with a steel headframe and hoisting plant, but the copper distribution proved to be lower in grade and more irregular than on neighboring properties operated by the Calumet and Hecla Mining Company, which eventually absorbed the Laurium acreage. Due to these challenging economic conditions and the high cost of deep underground extraction, regular corporate mining was suspended in 1913, with sporadic exploration and final cleanup work continuing until the property was permanently closed in 1914.

Questions about this specimen?
Send an email or call us: 314-341-1811.