Wulfenite with Goethite Mottramite and Smithsonite

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Yet again a fascinating specimen from the Tsumeb mine comes into our possession, the like of which I have never seen. This is why Tsumeb is so remarkable because it keeps throwing-up surprises even after having been closed for over twenty years! Good-sized flat, tabular crystals of wafer-thin Wulfenite are completely coated with a thin veneer of mammillary Goethite, imparting a colour which grades from light milk-chocolate-brown to dark-chocolate. Just ensure you don't eat it! This complex specimen is also overgrown with botryoidal greenish-grey Mottramite and micro-rhombic crystals of glassy pale lemon Smithsonite. This specimen could be studied closely for an hour and continue to revel its secrets! Under magnification and at occasional places where a Wulfenite crystal is slightly chipped, the internal fibrous crystalline structure of the Goethite can be seen radiating out from the glassy butterscotch Wulfenite plates. This is a perfect example of how an epimorph forms. If at some later stage the Wulfenite had been dissolved out, the Goethite would have remained as we now see it, but in the habit of tabular crystals. The largest Goethite-covered Wulfenite measures 2.4 x 2.1 x 0.1 cm. This is a wonderful specimen, remarkably different to the many thousands of specimens I have handled from Tsumeb and one that will make a superb addition to the best of Tsumeb collections.

Origin: Tsumeb Mine, Otjikoto Region, Namibia