Mineral: Azurite
Chemistry: Cu3(CO3)2(OH)2
Size: 25 mm (largest); and 18 mm
Owner: Harald Muench
Photographer: Jeff Scovil

The photograph shows two small, but remarkable specimens of azurite.

Twinning is rare in azurite (Palache et al., 1951), but is occasionally observed on (-101), (-102) or (001),  Twinned azurites from Tsumeb, however, are exceptionally rare, such that Palache and Lewis (1927), after examining some 1500 specimens of azurite from Tsumeb reported that "no twinned crystals were observed". 

The two specimens shown here are twinned azurite crystals.  In each case, the individuals are elongated on the c-axis, [001], and appear to be twinned on (-102), as shown in the accompanying drawing.  The overall habit of these specimens, resembles the Japan Law twinning that is sometimes observed in quartz.

These are two (from a total of three) specimens, all similar and presumably from the same occurrence, purchased by the current owner from Windhoek dealer Sid Pieters, in 1976. Unfortunately the location in the mine from which they were recovered is not known.