Arsentsumebite, (w. Bayldonite, after Azurite)

Size: 36 mm
Owner: Mariusz Oleszczuk
Photographer: Mariusz Oleszczuk

A pseudomorph of bright apple-green arsentsumebite, with bayldonite (both XRD verified), after azurite.  The original form of the azurite crystals is very sharply preserved, leaving little doubt as to the identity of the precursor mineral.

Arsentsumebite and bayldonite are both lead-copper arsenates, and XRD analysis has shown that both occur in this replacement, although the proportions of the two minerals has not been quantitatively determined.

While arsentsumebite, bayldonite and azurite are all common minerals in Tsumeb's first oxidation zone, the replacement of azurite by these arsenates is rarely encountered in such well-defined examples.