Copper

specimen number:
2102284

location:
Mountain City Mine, Elko Co., Nevada, USA

description:
Quite nice for this old locality, and aesthetic branching crystallized grouping of native copper without matrix. In good condition all around.

The Mountain City Mine, also known as the Rio Tinto Mine, is located in Elko County, Nevada, and stands as one of the most significant copper discoveries in the history of the state. Geologically, the deposit is a massive sulfide body hosted within the Paleozoic-age Valmy Formation, specifically where quartzites and shales were enriched by secondary copper mineralization. The site is notable among collectors for producing crystallized copper, which often appears as sharp, arborescent (tree-like) branching structures or thick, distorted masses with a deep metallic luster. Historically, the deposit was discovered in 1931 by SF Hunt after years of prospecting, leading to a major mining boom during the Great Depression. Industrial underground mining and quarrying operations were conducted primarily by the Rio Tinto Copper Company and later the Anaconda Copper Mining Company between 1932 and 1947. During its peak years of operation, the mine was one of the highest-grade copper producers in the United States, yielding significant quantities of ore before the primary deposit was exhausted and the mine closed in the late 1940s. Today, the site is remembered for its rapid rise to prominence and the high-quality native copper specimens it provided to the mineralogical community.

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