Carbonate Group Visible Spectra (350 - 1100 nm)

The common colored carbonate minerals are calcite, CaCO3, ankerite, FeCO3, and rhodochrosite, MnCO3.

The color of calcite can be due to its iron content which is present as Fe2+, to Mn2+, to radiation damage centers which often involve rare-earth or other elements, or occasionally to other elements such as Co2+ in what is commonly called cobaltian calcite.

Siderite owes its color to Fe2+

The color of rhodochrosite is due to its Mn2+ content. Most minerals with Mn2+ in six-coordination are pale pink. Because Mn2+ does not absorb light strongly, a mineral must have a high Mn2+ concentration to be strongly colored by Mn2+. Because some rhodochrosite specimens have a high degree of transparency, light can penetrate deep into the crystal and be highly absorbed in the appropriate wavelengths. 

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