SILVER & ACANTHITE ON CALCITE

ABOUT THE SPECIMEN

Leaf-like growths of crystalline silver popping out of white calcite, all on top of a plate of acanthite. I've seen a lot of specimens from this locality with silver lightly draped over matrix, this one is exceptionally three-dimensional by comparison. One branch of silver is protruding upwards with a crystal of acanthite at the top, delicately balanced for a rich addition to the assemblage. Fantastic luster throughout as well as UV reactivity in the calcite makes this a fine specimen from a great silver locality.

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Bouismas is one of the easternmost workings in the Bou Azzer district, a Neoproterozoic five-element vein-type deposit in which Co-Ni arsenides, native silver, and bismuth mineralized in fractures cutting serpentinized Precambrian peridotite - the world's only major cobalt district where the metal is mined as a primary commodity rather than a byproduct. Silver at Bouismas occurs in a distinct sulfide-sulfosalt stage overprinting the earlier arsenide mineralization, with Mindat documenting a silver-rich vein worked from mid-2008 through spring 2010 that also produced partial pseudomorphs of allargentum and minor dyscrasite. Native silver from this window formed as arborescent and dendritic growths on white calcite matrix; a subset shows cubic and spinel-twinned crystals of unusual sharpness for the species. Most specimens arrived encased in calcite requiring careful mechanical preparation to expose the silver within. Proustite occurs as a notable associate on some matrix pieces, adding red sulfosalt contrast against the calcite. The documented production window was narrow and the vein is now exhausted, meaning all available material is fixed to what was recovered during those roughly two years of activity - a tight supply that has kept Bouismas silver consistently underrepresented in Western collections relative to its quality.