Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its (rare) pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. It streaks white, and its Mohs hardness varies between 3.5 and 4. Its specific gravity is between 3.5 and 3.7. It crystallizes in the trigonal system, and cleaves with rhombohedral carbonate cleavage in three directions. Crystal twinning often is present. It is transparent to translucent with refractive indices of nω=1.814 to 1.816, nε=1.596 to 1.598. It is often confused with the manganese silicate, rhodonite , but is distinctly softer. It is officially listed as one of the National symbols of Argentina.
Rhodochrosite forms a complete solid solution series with iron , (as well as magnesium , to a limited extent) frequently substitutes for manganese in the structure, leading to lighter shades of red and pink, depending on the degree of substitution. It is for this reason that the most common color encountered is pink.