aragonite

Pseudo-hexagonal trillings of aragonite (to 14 mm), free standing and randomly orientated on a fragment of dolostone matrix. The trillings are colourless-white and variously transparent with some crystals quite gemmy while others are moderately turbid.

An old MGMH label describes this as “Aragonite containing zinc” (Exhibit 2) and a handwritten note (Exhibit 3) names the specimen as “nicolsonite [sic.]”, apparently on the basis of a specific gravity determination. SEM/EDS analysis (Frank Keutsch, Harvard University 2025) confirms, however, that there is essentially no Zn in the aragonite but that it contains approximately 10 wt % Pb.

The specimen is from the collection purchased by Charles Palache during his visit to Tsumeb in December 1922, which dates it to the upper part of the first oxidation zone (i.e. 8 Level or above).