Aragonite

cerussite; goethite; smithsonite

cerussite; goethite; smithsonite

An isolated group of free-standing, ivory-white aragonite trillings (to 30 mm) on a crust of yellow-brown iron-stained smithsonite over a shard of oxidising sulphide ore. A single crystal of colourless cerussite (6 mm) occupies a vug at the junction of the smithsonite and the oxidising sulphide. The aragonite has not been analysed, but it has the colour and habit (reverse taper) typically associated with the lead-bearing variety tarnowitzite; interestingly, however, it was labelled as “nicholsonite” (the zinc-bearing variety) by its original owner, probably on account of its density.

The specimen was number 4339 in the collection of Austrian industrialist Hans von Karabacek, part of which was purchased by Harvard University in 1935. This unequivocally dates the specimen to the first oxidation zone.