By a simple washing of vaterite with ultrapure water, it transforms rapidly into cubic calcite. When the solid is washed with Cu 2+ solutions, the transformation depends on the concentrations of the copper solutions applied in the process. For concentrations of 10 -4 mol dm -3 , a certain delay in the transformation process is detected, and the obtained cubic calcite seems to be in the form of Cu x Ca 1-x CO 3 . For concentrations of 10 -3 mol dm -3 , the vaterite structure remains stable with time, and this stability seems to be correlated with the saturation of the surface by Cu 2+ in place of Ca 2+ . For concentrations of 10 -2 mol dm -3 , a mixture of vaterite, aragonite, cubic calcite, and malachite is obtained during the transformation process.

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Be thune, lÏUniversite , c L aboratoire de Catalyse et URA 402 CNRS, U.S.T .L (L ille I) 59655 He te roge`ne Homoge`ne, V illeneuve dÏAscq Cedex, France d L aboratoire de Catalyse et Environnement, MREID, du dÏOpale, 145 Universite L ittoral-Coü te Route du Pertuis dÏAmont, 59140 Dunkerque, France formation of solid solution and (ii) thereby explains the apparent stabilization of MnII-doped vaterite observed Mn x Ca 1~x CO 3 , experimentally.