Calcite, (w. Dioptase)

Mineral: Calcite, Dioptase
Chemistry: CaCO3
Size: 128 mm
Owner: Geoff Krasnov
Photographer: Geoff Krasnov

A group of sharp, intergrown calcite rhombs (to 25 mm). The cleaved crystal near the base of the specimen shows that the cores of the calcite are pinkish-red in colour, presumably due to the presence of tiny quantities of hematite (?).

However, during the latter stages of calcite formation, microcrystalline dioptase has precipitated simultanaeously with the calcite, so that the outer zone of each calcite crystal is richly included and coloured by the copper silicate.