Chalcosiderite

specimen number:
1052741

location:
Wheal Phoenix, Linkinhorne, Cornwall, England, UK

description:

Extremely fine and richly crystallized example for this Cornish classic. Lustrous deep green chalcosiderite throughout matrix. In good condition. The specimen comes with an antique label as shown at the end of the video. The specimen was originally acquired in 1907.

The Wheal Phoenix mining complex, situated on the southeastern slopes of Bodmin Moor near Linkinhorne in Cornwall, England, was a major underground copper and tin operation that ranked among the most productive mines in the Caradon mining district. Geologically, the deposit is located along the structural margin of the Bodmin Moor granite pluton, an Early Permian-age igneous intrusion that drove widespread hydrothermal mineralization into the surrounding Devonian-age sedimentary rocks, locally termed killas. Hydrothermal fluids circulating through deep-seated fault fissures deposited rich, steeply dipping quartz-chlorite veins containing primary chalcopyrite, cassiterite, and pyrite, with extensive near-surface supergene oxidation producing exceptional pockets of secondary copper and iron minerals, notably malachite and chalcosiderite. Historically, while localized surface tin streaming occurred on the moor for centuries, large-scale industrial underground mining commenced in 1836 under the direction of mining engineer James Seccombe after rich copper lodes were discovered. The mine operated with great success through the mid-nineteenth century, expanding significantly in 1865 through a merger with the adjacent Wheal West Phoenix to form the Phoenix United Mines, which utilized heavy steam-powered pumping and winding engines to reach depths of nearly four hundred meters. Falling copper prices in the late 1870s forced a structural transition toward deep tin extraction, but diminishing reserves and rising operational costs eventually led to the total cessation of commercial operations and permanent closure of the mine in 1898, with the historic engine houses and granite ruins remaining preserved as part of a UNESCO World Heritage site through 2026.

J. Brunner was a notable German mineral dealer based in Magdeburg during the late 19th and early 20th centuries, a period when the city served as a significant hub for European trade and industry. His dealership was recognized for supplying high-quality mineralogical and geological specimens to both private collectors and academic institutions, often focusing on the diverse mineral wealth of the Harz Mountains and the Stassfurt salt deposits. Historically, Brunner played a role in the wider distribution of rare species and classic German locality pieces, with his name frequently appearing on historical specimen labels that are still preserved in museum archives.

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