Dioptase (w. plancheite)

calcite (?); plancheite; quartz

Emerald-green crystals of dioptase are scattered sparsely over a crust of pale-blue plancheite (XRD verified). The size distribution of the dioptase crystals is bimodal, with a very few individual crystals (to 8 mm) standing prominently on the plancheite and contrasting with localised aggregates comprising numerous sub-mm crystals. The plancheite forms a sub-botryoidal crust on the surface of a siliceous, quartz-rich matrix. Sparse aggregates of colourless-white calcite (?) are also present on the plancheite.

The specimen was formerly in the collection of Franz Lammer, who's label indicates that he purchased it from Sid Pieters in Windhoek, Namibia (Exhibit 2).