Alabandite

Alabandite, a manganese sulphide with the formula MnS, is rarely seen in good specimens, so this part, yet very sharp, octahedral crystal is a superb example of the species.  From the pegmatite veins and hydrothermal fracture fillings in the Merelani Hills, in the Simanjiro District of Tanzania, this entire specimen forms part of a large octahedral crystal with edges modified to the dodecahedron The crystal is steely grey-black with a sub-metallic.