Rhodochrosite (Wessels Mine) 40mm x 30mm x 14mm.
Wessels Mine, Kalahari Manganese Fields, South Africa. 40mm x 30mm x 14mm.
These are rare, they came from the old Wessels mine and even then where considered unique. The cubic form of Rhodochrosite is not common from the Kalahari Manganese Fields. Between the cubes the other mineral is black Manganite. Note the additional close up images better displaying the crystal structures.