Calcite, nailhead.

Calcite, nailhead.

Calcite, Calcium carbonate , CaCO3  Calcite is a very common mineral, found in nearly all geologic environments. This specimen is a druse of "nailhead" calcite crystals, on a rhodochrosite base. The crystals have a dusting of a black mineral, probably goethite. The rhodochrosite shows just a hint of pink colouration in places. It was collected from South mine, Broken hill, New South Wales, Australia.