Mottramite with Calcite

specimen number:
2133290

location:
Tsumeb Mine, Otjikoto, Namibia

description:
Sparkling deep green crystallized mottramite across the front of matrix with calcite. In good condition.

The Tsumeb mine, situated at the northern margin of the Otavi Highland within the Oshikoto Region of Namibia, is a legendary and deeply historic underground operation globally celebrated for producing an astonishing array of secondary minerals, including exceptional, world-class crystal aggregates and deep forest-green botryoidal crusts of the copper-lead vanadate mottramite. Geologically, this incomparable deposit consists of a massive, steeply dipping mineralized pipe structure hosted within Upper Proterozoic-age dolomites and limestones of the Otavi Group. The pipe was formed by an ancient, mineral-rich hydrothermal solution flowing through a collapsed dissolution collapse breccia structure, which deposited deep-seated primary lead, copper, and zinc sulfides that were subsequently subjected to millions of years of intense, multi-stage supergene alteration and deep groundwater oxidation. This prolonged weathering process deeply altered the carbonate host rock and reprecipitated highly oxidized zinc, lead, and vanadium ions, allowing magnificent, mirror-lustrous, and micro-crystalline coatings of mottramite to form beautifully inside porous solution cavities alongside malachite, azurite, and mimetite. Historically, organized industrial development and underground shaft-sinking commenced around 1900 under the Otavi Minen- und Eisenbahn-Gesellschaft (OMEG), supplying immense quantities of base metals through two world wars before the complex was acquired in 1947 by the Tsumeb Corporation Limited (TCL), which pushed the underground workings to a depth exceeding 1,500 meters. Continuous large-scale extraction ran until severe labor strikes, flooding, and economic exhaustion forced the permanent closure of the main industrial mine in 1996.

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