azurite (on smithsonite)

cerussite; smithsonite

A plate of botryoidal smithsonite, very pale straw-yellow in colour but with a subtle and localised pink blush, hosts equant crystals of lustrous blue-black azurite (to 10 mm) and two small reticulated aggregates of colourless cerussite, the larger of which measures 7 mm across (Exhibit 2). A rib of sulphide matrix adheres to the reverse of the specimen with very minor malachite on its surface. The azurite crystals, however, are completely free of malachite alteration.

The specimen was number 1810 in the collection of Austrian industrialist Hans von Karabacek, part of who’s collection was purchased for Harvard University in 1935. The specimen is therefore unequivocally from the first oxidation zone.