Copper

specimen number:
8311517

location:
Nebraska Mine, Ontonagon Co., Michigan, USA

description:

A very large crystal of native copper 3.5 cm in size coming off of a grouping of crystallized native copper. In great condition, really impressive crystal size on this one.

The Nebraska mine, situated near Mass City in Ontonagon County within the historic western Upper Peninsula copper district of Michigan, United States, was a pioneering mid-nineteenth-century underground operation celebrated for its early extraction of native metals and its remarkable prehistoric heritage. Geologically, this deposit is hosted within the Mesoproterozoic Portage Lake Volcanics of the Midcontinent Rift system, where copper-bearing hydrothermal fluids mineralized the porous, vesicular, and fragmental amygdaloidal tops of subaerial basalt lava flows, specifically concentrating native copper and native silver alongside secondary minerals like epidote, microcline, quartz, and adularia. Historically, the site was initially utilized thousands of years ago by ancient Native Americans, who left behind a dense line of primitive pits and stone hammerstones to extract surface copper from the weathered hillside. Modern industrial exploitation began when the Nebraska Mining Company was formally organized in 1853, with miners driving two adits into the ridge by 1854 and subsequently sinking three vertical shafts to extract rich mass and barrel copper. Following a severe economic depression in 1858, the company scaled back its operations and leased portions of the property to independent tributor miners until 1863, when the company reorganized and merged with the adjacent Caledonia Mine to form the New Caledonia Mining Company, leaving the underground workings of the two properties interconnected. Through 2026, while commercial underground operations have long been dormant and the property remains under private exploration ownership, the Nebraska mine remains an important regional archaeological and geological benchmark for studying early primitive mining technology and the classic stratiform native copper mineral lodes of the Keweenaw Peninsula.

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