aragonite

malachite

A large plate of free-standing, pseudo-hexagonal aragonite trillings (to 18 mm) on altered dolostone. The aragonite crystals are essentially prismatic in habit, but with a slight reverse taper (i.e. widening towards the terminations). Very minor malachite is associated, both between the aragonite crystals and on the dolostone matrix. EDS analysis shows that the aragonite contains circa 5 wt % Pb and essentially no zinc (Frank Keutsch; Harvard University, 2025).

The specimen is from the collection of Wilhelm Klein, production manager at Tsumeb between 1916 and 1939. Unfortunately, Klein’s number is missing from this specimen; all the aragonites in his catalogue, however, are attributed to levels 11 through 14, providing circumstantial evidence it was recovered from the deeper part of the first oxidation zone.