Rhodochrosite has a variable chemical composition. It is a manganese carbonate, but the manganese is frequently replaced by iron, magnesium and/or calcium as shown in this formula: (Mn,Fe,Mg,Ca)CO3.
These substitutions of other elements for manganese change the composition and alter the specific gravity, hardness, and color of the mineral. The bright pink color can become grayish, yellowish, or brownish in response to this chemical variability. A complete solid solution series exists between rhodochrosite and siderite (FeCO3).
Rhodochrosite is generally easy to identify and is rarely confused with other minerals. Its pink color, perfect cleavage in three directions, low hardness, and weak effervescence with cold dilute hydrochloric acid are rarely seen in other minerals.
The most common confusion is between the names “rhodochrosite” and “rhodonite” — both are pink, manganese-rich minerals with very similar names that people have a hard time remembering.
| Physical Properties of Rhodochrosite | |
| Chemical Classification | Carbonate |
| Color | Pink, red, yellow, gray, brown |
| Streak | White |
| Luster | Vitreous to pearly |
| Diaphaneity | Transparent to translucent |
| Cleavage | Perfect, rhombohedral, in three directions |
| Mohs Hardness | 3.5 to 4 |
| Specific Gravity | 3.5 to 3.7 |
| Diagnostic Properties | Pink color, cleavage, hardness, effervescence in cold dilute hydrochloric acid |
| Chemical Composition | (Mn,Fe,Mg,Ca)CO3 |
| Crystal System | Trigonal |
| Uses | Ore of manganese, gemstone, ornamental stone |