Mineral: Aragonite
Chemistry: CaCO3
Size: 95 mm
Owner: Harvard University (Karabacek Collection)
Photographer: Malcolm Southwood

An isolated group of free-standing, bright, pearly-white crystals of aragonite (to 30 mm), on a contrasting orange-brown limonitic matrix. The specimen is from the first oxidation zone, and is number 4339 in the Karabacek collection, where it is labelled as "nicholsonite" (i.e. the zinc-rich varietal of aragonite).  However, the colour and the habit, with the crystals showing the characteristic taper towards the base, are strongly suggestive of the lead-rich variety, "tarnowitzite" (?).

Courtesy  of  the  Mineralogical  &  Geological  Museum  at  Harvard  University,  Aragonite; MGMH  ID# 93440, Tsumeb; Namibia. @ copyright 2012, President and Fellows of Harvard College. All rights reserved.