Brochantite, (after Azurite)

Mineral: Azurite, Brochantite
Size: 30 mm
Owner: John Schneider
Photographer: John Schneider

This intriguing specimen is a pseudomorph of brochantite (analytically verified) after what was probably azurite (?), on a matrix that appears to include copper arsenates and possibly a little malachite (?). It is not clear whether this is a complete replacement, or simply an encrustation pseudomorph but, other than shape, there is little to indicate the identity of the parent mineral.

Pseudomorphs of brochantite after azurite (Weber, 1977), and after gypsum (Gebhard, 1999) have been reported, but both are regarded as rare.  Both azurite and gypsum are monoclinic and, in any event, the shapes of the pseudomorphs in this specimen are insufficiently sharp to be diagnostic.  On balance, brochantite after azurite seems to be the most plausible description but, as with so many pseudomorphs, the identity of the parent mineral is uncertain.