Copper

specimen number:
2062192

location:
Gull Rock Fissure, Keweenaw Co., Michigan, USA

description:

Collected from this underwater locality in 2001, a beautiful cluster of twinned native copper crystals without matrix. In super condition.

The Gull Rock Fissure, located on the northern tip of the Keweenaw Peninsula near Manitou Island in Michigan, is a remarkable example of a submerged native copper deposit. Geologically, it is a narrow, mineralized fissure vein that cuts through the Precambrian basaltic lava flows of the Portage Lake Volcanics, a part of the Midcontinent Rift System. The fissure is famous for containing pure native copper, often occurring as jagged, compressed masses or robust branching forms that were preserved in the cold, clear waters of Lake Superior. Historically, the site was never a commercial mine in the traditional sense due to its location beneath the lake surface, but it has been a target for marine salvage and mineral exploration since the mid-19th century. Significant recovery efforts occurred in the late 19th century and again by specialized divers in the late 20th century, specifically during the 1970s and 1980s, to retrieve large masses of copper from the lake bed. Today, specimens from Gull Rock are highly prized by collectors for their unique underwater provenance and the distinct, rugged character of the native copper found within this narrow geological fault.

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