Arsentsumebite after Mimetite

specimen number:
2072213

location:
Tsumeb Mine, Otjikoto, Namibia

description:
Small prismatic crystals of what were once mimetite across the front of this matrix, these now replaced by arsentsumebite. Some damage present as seen, still quite nice for one of these classics.

The Tsumeb Mine, located in the Otavi Mountainland of northern Namibia, is a legendary polymetallic deposit renowned for its remarkable mineral diversity. Geologically, it is a pipe-like structure hosted within Neoproterozoic dolostones of the Otavi Group, where mineral-rich hydrothermal fluids replaced karst features to form massive sulfide ore bodies. The site is particularly famous for its complex oxidation zones which facilitated the formation of rare secondary minerals and spectacular pseudomorphs, including arsentsumebite after mimetite. In these occurrences, the original yellow or green mimetite crystals are chemically replaced by apple-green to sky-blue arsentsumebite, often perfectly preserving the original hexagonal prismatic habit of the mimetite. Historically, industrial mining commenced in 1900 under German control and continued through various iterations of the Tsumeb Corporation Limited. The mine remained a global powerhouse for lead, copper, and zinc production for nearly a century until its final closure in 1996 due to flooding and the exhaustion of accessible ore reserves, leaving behind a legacy as the world's premier mineral locality.

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