Rhodochrosite is a pink colored manganese carbonate mineral which forms a concentric banded structure like that found in stalactites which are made of calcite.
The Argentine material comes from the Capillitas Mine in the Catamarca Province. This is an old Inca silver mine located away up in the Andes at over 3000 meters altitude, with over 30 kilometers of tunnels.
Rhodochrosite also occurs rarely as transparent single crystals from which facetted gemstones can be cut. Most gem dealers have rhodochrosite for sale.