Azurite, (w. Cerussite, Malachite, and Rosasite)

Chemistry: Cu3(CO3)2(OH)2
Size: 120 mm
Owner: Malcolm Southwood
Photographer: Olga Kaspera / Malcolm Southwood

This specimen is from a small but distinctive first oxidation zone pocket, believed to have been mined in the 1920s.  It shows a particularly diverse paragenesis of carbonate minerals.  The matrix is an altered dolostone, with a thin crust of very pale-green smithsonite, largely obscured by a surface veneer of a pearlescent white carbonate which is probably dolomite (?).   The lower two-thirds of this matrix (as seen in the main photo) has been overgrown by a mat of blue-green spheroidal aggregates (to 1 mm) of rosasite.  Completing the assemblage are numerous crystals of colourless-white, glassy, twinned cerussite (to 9 mm), and somewhat more sparsely distributed crystals of highly lustrous, blue-black azurite. 

The prominent azurite crystal (43 mm) is interesting because it comprises a thin overgrowth of second-generation azurite on a pre-existing pseudomorph of malachite after azurite; the crystallographic orientation of the azurite overgrowth appears to be identical to that of the first generation crystal.  Such overgrowths were apparently quite commonly encountered in the first oxidation zone during the1920s and are described in detail by Palache and Lewis (1927).  

This specimen is one of two from this pocket that were in the collection Franz Lammer (Austria; see label), which originated from the personal collection of Austrian dealer Anton Berger (1870-1956).  Only a few specimens from this pocket are known and most, if not all, of them appear to have been brokered by Berger; the best-known example is in the Karabacek collection at Harvard Univerity; Hans Karabacek was a major customer of Berger's in the 1920s and early 1930s.