RHODOCHROSITE

(Greek: Rose Coloured), mineral composed of manganese carbonate (MnCO3) that is a source of manganese for the ferromanganese alloys used in steel production. It is commonly found in ore veins formed at moderate temperatures, in high-temperature metamorphic deposits, and in sedimentary deposits. Notable localities are Cavnic, Romania; and Butte, Mont., and Leadville, Colo., in the United States. Magnesium, iron, and calcium are generally partially substituted for manganese, pure rhodochrosite being relatively rare; rhodochrosite forms a partial solid-solution (chemical substitution) series with calcite and with siderite in which calcium and iron, respectively, replace manganese in the crystal structure. For detailed physical properties, see carbonate mineral (table).