MODEL STUDY OF THE 1ST STEPS IN THE DETERIORATION OF CALCAREOUS STONE.3. MANGANESE AND IRON-MEDIATED SULFATION OF NATURAL STONE

Transition-metal-mediated sulphation of calcareous stone is investigat ed. Mixes of iron and manganese compounds with precipitated or ground calcite are employed to model natural calcareous stones containing the se metals in trace concentrations. The products are characterized by D iffuse Reflectance Infrared Fourier Transform spectrometry. Sulphation is shown to depend strongly on the amounts of transition metals in th e mixture, and calibration curves are constructed. Sulphate formations at natural calcareous stone surfaces are discussed within the framewo rk of the assumed model.