Copper

specimen number:
8311314

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

description:

Superb well crystallized grouping of native copper, the largest crystals measuring to 3.5 cm in size. This is in super condition.

The National Mine, located in Ontonagon County, Michigan, was one of the premier producers in the Rockland district of the Keweenaw Peninsula. Geologically, the mine was situated on the famous Minesota Lode, a major strike-fault vein where native copper was deposited within a thick bed of conglomerate and along the contact with the underlying basalt. The site was renowned for producing massive quantities of "mass copper," including individual pieces weighing several tons that required specialized "sand blasts" to liberate from the host rock. Historically, the National Mining Company was organized in 1848 and began active operations in 1852. The mine enjoyed a highly profitable era during the mid-19th century, frequently paying out substantial dividends to its shareholders. After the initial rich deposits were depleted, the mine underwent various reorganizations and intermittent periods of activity before finally closing its main operations in 1893. Today, the site is a significant stop for historians and mineral collectors interested in the unique "mass copper" mining techniques of the early Lake Superior copper boom.

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