Calcite, (w. Dioptase)

Mineral: Calcite, Dioptase, Duftite
Chemistry: CaCO3
Size: 59 mm
Owner: Trinity Minerals
Photographer: John Veevaert

Early-formed rhombohedral crystals of calcite are encrusted with emerald-green dioptase crystals, and then partly overgrown by a second generation of colourless-white, translucent calcite with the same orientation as the first generation.  

The included dioptase provides colour to the outer layer of calcite but, where this layer failed to develop, the dioptase encrustation is directly visible,  A little apple-green duftite (?), best seen in Photograph 2, provides an attractive colour accent.

The specimen is from the second oxidation zone.