Calcite, (w. Cuprite and Malachite)

Chemistry: CaCO3
Size: 80 mm
Owner: Kalahari Classics
Photographer: Kalahari Classics

A very colourful calcite specimen, with a complex paragenesis.  

The first generation of calcite comprises a layer of intergrown crystals extensively coloured blue-green by minute inclusions of dioptase, and partly overgrown by an earthy apple-green crust of duftite/conichalcite (?).  

The second calcite generation consists of sharp rhombohedral crystals (to 13 mm).  The cores of these crystals are coloured bright orange-red by tiny inclusions of cuprite (v. chalcotrichite), while the outer zones are colourless, glassy and highly transparent.  However, these colourless outer zones are included by aggregates of acicular, lustrous green malachite, many of which display a "bow-tie" habit.  Typically, the malachite aggregates are only partly enclosed in the calcite, with the green fibrous aggregates protruding from many of the calcite faces (photographs 3 and 4).

(FOV for Photograph 2 is c. 25 mm;  FOV for Photograph 3 is c. 18 mm;  FOV for Photograph 4 is c. 12 mm)