Heterogenite and Calcite with Duftite

Item Description

A very unusual Tsumeb piece for its mineralogy and paragenesis. This is a fine heterogenite specimen AND a fine calcite specimen at the same time - This remarkable Jekyll and Hyde piece from Tsumeb is like no other we have seen from this famous locality! The two sides are so conspicuously different with the Hyde side completely dominated by glossy, black-green botryoids of Heterogenite and the Jekyll side by translucent, white rhombs of Calcite dusted with Duftite. Heterogenite is an uncommon cobalt hydroxide and forms as a secondary alteration of primary cobalt-bearing ores. It is usually a "coating" or the ugly side mineral covering up something more beautiful, but in THIS case, it is a really attractive piece! It's apparent that the Heterogenite formed early and Calcite was subsequently deposited on the Calcite followed by discontinuous patches of light olive green Duftite. Very trivial but some small bruising to both the Heterogenite and Calcite is noted, but only discernible up close and it shows off so nicely that, as a specimen for this species in a Tsumeb suite, I can quite easily accept any small bruises. Hard to value such a unique piece - there are no comparables!

This specimen is part of the 2022 Dallas Mineral Collecting Symposium benefit auction, with proceeds benefiting Mineralogical Record, Rocks & Minerals, Tucson Gem and Mineral Society, and mindat.org. Thanks to all of our participants!

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