Copper

specimen number:
8311101

location:
Copper Falls Mine, Keweenaw Co., Michigan, USA

description:

Neat and aesthetic amygdaloidal crystallized pipes of native copper coming off matrix. In terrific condition. Complete all around.

Amygdaloid pipes in Michigan copper deposits are natural features formed in ancient basalt lava flows of the Keweenaw Peninsula. As the lava cooled, gas bubbles created rounded cavities called amygdules, which were later filled by mineral rich fluids depositing native copper and other minerals. In some areas these cavities became aligned along fractures or fluid pathways, concentrating mineralization into pipe like zones. The result is a tubular pattern of copper filled amygdules that reflects both the volcanic origin of the rock and the later movement of mineralizing fluids.

The Copper Falls Mine in Keweenaw County, Michigan, was one of the early copper mining operations developed on the Keweenaw Peninsula during the mid 1800s. Mining began around 1845 after native copper was discovered in fissure veins cutting the basalt flows of the Portage Lake Lava Series. The mine was worked through underground shafts and drifts that followed the copper bearing veins. Although production was limited compared to larger nearby mines, Copper Falls was part of the early wave of exploration and development that helped establish the Michigan copper industry.

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