Stability relations among minerals in the system CaSiO₃-FeSiO₃-MnSiO₃-H₂O have been determined experimentally by means of ion exchange at 600°C and 1kbar. Aqueous chloride solution was used as a transport and exchange medium for cations. Stable minerals under the experimental conditions are wollastonite, bustamite-ferrobustamite solid solution, hedenbergite, pyroxmangite, rhodonite and fayalite+quartz instead of ferrosilite. Bustamite occupies a wide stability field along the CaSiO₃-MnSiO₃ join, and forms a continuous solid solution with ferrobustamite. Both pyroxmangite and rhodonite have elongated stability fields parallel to the FeSiO₃-MnSiO₃ join. The mineral assemblages hedenbergite+bustamite+fayalite+quartz and bustamite+pyroxmangite+fayalite+quartz were confirmed to be stable under the experimental conditions. Ferrous and manganese ions are preferentially incorporated into the solid phases in contrast to calcium ion.