Copper

specimen number:
8311538

location:
White Pine Mine, Ontonagon Co., Michigan, USA

description:

Beautiful branching crystallized native copper specimen. Aesthetic and in great condition all around.

The White Pine mine, situated near the south shore of Lake Superior in Ontonagon County within the western Upper Peninsula of Michigan, United States, was a massive industrial underground operation that stood out as the largest known sediment-hosted copper-shale deposit in the nation. Geologically, this immense stratiform ore body is located at the contact boundary between the Mesoproterozoic-age Copper Harbor Conglomerate and the overlying Nonesuch Shale, both of which filled a deep basin within the Midcontinent Rift System approximately 1100 million years ago. While the surrounding Keweenaw Peninsula is legendary for pure native copper lodes, the White Pine deposit is mineralogically unique because its primary ore is dominated by fine-grained chalcocite, a copper sulfide, along with native silver and native copper precipitated within organic-rich, dark gray siltstone and shale layers by migrating, metal-bearing hydrothermal fluids. Historically, early exploratory shafts were sunk at the site between 1880 and 1881, followed by a brief period of experimental native copper production by the Calumet and Hecla Mining Company from 1914 until low copper prices forced a total shutdown in 1921. The Copper Range Company purchased the dormant property in 1929 and spent over two decades developing an advanced flotation milling process to successfully separate the fine chalcocite particles, eventually securing a federal loan during the Korean War to build a sprawling modern industrial complex that poured its first commercial copper in January 1955. The operation expanded into a massive underground labyrinth employing thousands of workers and producing billions of pounds of copper until declining ore grades, high operational costs, and environmental challenges forced its official closure in September 1995. Through 2026, while the extensive underground workings remain completely flooded and commercial extraction is inactive, the White Pine site continues to undergo modern remediation assessments and remains a premier global geological benchmark for studying stratiform base-metal enrichment within ancient rift-related sedimentary sequences.

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