An intriguing specimen showing brown to yellowish Siderite with areas of pink Rhodochrosite. On the back, you can clearly see the gradual pseudomorphing process — where Siderite was slowly replaced by Rhodochrosite over time. It was found in 1998
Chemically, both minerals are carbonates with a similar crystal structure:
- Siderite: FeCO₃ (iron carbonate)
- Rhodochrosite: MnCO₃ (manganese carbonate)
Because iron (Fe²⁺) and manganese (Mn²⁺) have nearly identical ionic sizes and can substitute for each other in the crystal lattice, it’s common to see one mineral partially replacing the other. This creates transitional specimens like this one, where the two species coexist and record the gradual geochemical change from iron-rich to manganese-rich conditions during formation.
From the famous Mont Saint-Hilaire, Québec — known for its exceptional diversity and unusual mineral associations. 5.4 x 4.2 x 3.0 cm