Near-infrared (NIR) and X-ray fluorescence spectra were recorded for 15 different samples of marmora, from the Mediterranean Basin and of different colours. After appropriate pretreatment (SNV transform + second derivative), the results were subjected to principal component analysis (PCA) treatment with a view to differentiating them. The observed differences among the samples were chemically interpreted by highlighting the NIR wavelengths and minerals, respectively, contributing the most to the PCA models. Moreover, a mid-level data fusion protocol allowed integrating the information from the different techniques and, in particular, to correctly identify (based on the distance in the score space) three test samples of known type. Moreover, it should be stressed that positive results on the differentiation and identification of marmora were obtained using two completely non-invasive, non-destructive and relatively inexpensive techniques, which can also be used in situ.
Ancient pottery buried for a long period of time, undergoes mineral transformations and acquires physical properties that enable differentiation from recent imitations by means of instrumental analysis.It is well known that after firing, ancient pottery is subjected t o natural radiation by the combined action of internal radioactive impurities and those scattered through the environment.When this pottery is heated to temperatures higher than 300°C a thermoluminescence (TL) is emitted, as a result of electronic displacements from the lattice defects filled by the high energy radiation. TL is not present in modern imitations, thus it is a practical discrimination method. Moreover, it also permits a determination of the age of ancient pottery. This is possible assuniing that T L increases linearly in ancient pottery from zero at the time of firing t o the present value. The radiation dose received since firing is usually measured by comparing the natural T L with the additional TL induced by exposing the specimen t o a calibrated source of artificial radiation.Another change which has occurred in Eitruscan bucchero of central Italy since firing has been detected (Flamini et al. 1975, Francaviglia et d. 1975). Bucchero contains a constant amount of CaO (-2%.j> while the calcite content of Italian clays ranges from 7 to 33%, and is only rarely close to zero. The low CaO contents of Etruscan bucchero were interpreted as due to leaching of CaO produced by the thermal decomposition of calcite (CaC03 + CaO + CO2) during firing, through the reaction CaO + H2 0 + Ca(OH)21 which is favoured by prolonged contact with the ground water. In addition, decomposition of calcite and leaching of CaO would explain the typical porosity and the low density of Etruscan bucchero.Thermal studies will now be described that show how ancient bucchero and red pottery underwent other transformations since firing which have not occurred in modern imitations, and which therefore provide a basis for easy discrimination.
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