Calcite on Mottramite

A charming small thumbnail of deep terracotta-orange to cherry-red Calcite crystals clustered on top of intergrown spherical masses of lustrous metallic grey-black Mottramite from the Tsumeb mine in Namibia.  The colour and translucency of the Calcite crystals suggests ferric iron, Iron (III), to cause the pigmentation rather than disseminated copper or cuprite.  These crystals measure to around 9 mm and form complex flattened saucers.  Although commonly green, Mottramite can be black (or very dark green) at Tsumeb, and the highly lustrous speckled surface coating does hide the more typical light olive to pistachio-green Mottramite cores.  A terrific small thumbnail mounted on a square acrylic base.