Copper

specimen number:
2062287

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

description:
Branching of somewhat crude but very large crystals of native copper. The prominent crystal measures almost 3.0 cm in size. In great condition. Collected in 1998.

The Laurium mine, located just south of Calumet in Houghton County, Michigan, is a historic underground copper operation situated within the Keweenaw Peninsula native copper district. Geologically, the deposit is hosted within the Portage Lake Volcanics, a Precambrian sequence of amygdaloidal basalt flows interbedded with felsic conglomerates. Native copper mineralization occurred when deeply sourced, low-temperature hydrothermal fluids moved upward through these porous volcanic tops and conglomerate beds, precipitating elemental copper alongside calcite, epidote, pumpellyite, and quartz within the basalt gas cavities. The Laurium Mining Company was organized in 1895 to explore these horizons, and formal shaft-sinking operations began in 1909, targeting the Kearsarge amygdaloid lode. The mine operated three shafts and produced several million pounds of refined copper before declining ore grades and high operational costs forced the permanent closure of the facility in 1920.

Kinoite is a rare blue copper-calcium silicate mineral that crystallizes in the monoclinic system. Geologically, it forms as a secondary mineral in oxidized zones of copper deposits, typically precipitating within late-stage hydrothermal veins, vugs, and amygdules where it is found in association with native copper, apophyllite, quartz, calcite, and epidote. The mineral was first discovered in 1969 near Sahuarita in the Santa Rita Mountains of Pima County, Arizona, and was named in honor of Father Eusebio Francisco Kino, a pioneer Jesuit missionary of the Southwest. In the Keweenaw Peninsula of Michigan, kinoite occurs as micro-crystals forming blue coatings and crystalline linings inside the basaltic pockets of local native copper mines.

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