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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. The streak is white. Its Mohs hardness varies between 3.5 and 4. Its specific gravity is 3.5 to 3.7. It crystallizes in the trigonal system. The cleavage is typical rhombohedral carbonate cleavage in three directions. Crystal twinning often is present. It is transparent to translucent. It is often confused with the manganese silicate, rhodonite, but is distinctly softer.Rhodochrosite forms a complete solid solution series with iron carbonate (siderite). Calcium, (as well as magnesium and zinc, 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.Rhodochrosite occurs as a hydrothermal vein mineral along with other manganese minerals in low temperature ore deposits as in the silver mines of Romania where it was first found. (source: Wikipedia) Photo by Michael Marcotte (showing red crystals of Rhodochrosite on a matrix of quartz) Above third specimen from Home Sweet Home Mine, Mt. Bross, Alma Dist., Park Co., Colorado. (Photo couretsy Heritage Auctions) Return to List Back to Michael's Hobbies page Back to Michael Marcotte's HomePage