Abstract: A stable rhodochrosite comprising manganese carbonate (MnCO3) and 0.03-0.3 wt % of an anion or ligand of phosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), an organic acid, or a salt of such acids, or 0.03-0.3 wt % of a mixture of such anions and/or ligands. Also, a method of producing stable rhodochrosite comprising manganese carbonate (MnCO3) in which a rhodochrosite comprising manganese carbonate (MnCO3) is treated by applying an aqueous treatment solution of phosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), sulfuric acid (H2SO4), an organic acid, or a salt of such acids, or a mixture thereof and the treated rhodochrosite is dried to produce stable rhodochrosite.