Contribution for a mineralogical thermometer to be applied to low fired and/or non-carbonate ceramics.

This research project was suggested by the need to define the ceramic firing temperature in some particular situations, such as non-carbonate ceramic pastes and lowsituations, such as non-carbonate ceramic pastes and low fired bodies (about 650 °C). This last condition is very frequent in the case of prehistoric artefacts, while noncarbonate pastes are frequently encountered in classic and medieval ceramics. The firing temperature is usually evaluated through the mineralogical transformations which occur in carbonate mixtures. But this method cannot be used in our case because no distinct crystalline phases were formed during firing, so the samples were analyzed by the usual techniques for chemical (XRF) and mineralogical (XRD) characterization and through innovative techniques such as micro-Raman and Mössbauer spectroscopy. The Raman technique allowed us to identify individual phase changes through the study of the evolution of vibrational spectra of titanium compounds, in particular, the transformation anatase/rutile. The use of Mössbauer spectroscopy is related to the presence of iron oxides and oxy-hydroxides. So, it was possible to verify the deviation of the magnetic properties of these compounds according to the effects of temperature on particle size and/or isomorphous substitution of iron by other elements that affect the Mössbauer spectra. In order to obtain reference data, two sets of laboratory specimens, made with an illitic and a kaolinitic clay, were prepared appropriately and characterized.