tsumebite (w. azurite and smithsonite)

Blocky crystals (to 10 mm) of lustrous blue-black azurite, on a crust of off-white smithsonite over a dolostone breccia. Locally, the smithsonite is quite richly encrusted with pale sea-green microcrystals of tsumebite.

The specimen is from the Hans von Karabacek Collection, much of which was acquired by MGMH in 1935. The vintage of the specimen dates it unequivocally to the first oxidation zone. A handwritten note records that this specimen was the source of crystals studied by LaForge (1938) to confirm that tsumebite crystallises with monoclinic symmetry.

azurite; smithsonite