ARCHAEOMETRICAL ANALYSES OF GLASS CAKES AND VITREOUS MOSAIC TESSERAE FROM MESSINA (SICILY, ITALY)

We report the results of a study performed on several glass samples recovered after the destructioncaused in Messina by the earthquake of 1908, and stored in the ‘Fiore’ deposit of the Regional Museumof Messina (Italy). The samples, still lacking a reliable classification, are glass cakes, some spare mosaictesserae, and fragments of a well-dated mosaic (Mosaico dell’Angelo, XIII–XIV century A.D.). EPMA,SEM-EDS, XRPD and XAS were employed to provide a detailed chemical, mineralogical and spectroscopiccharacterization of the samples. The chemical analyses of major elements show high levels of K2O andMgO, as a result of the prevalent use of plant ashes as flux. The cakes are characterized by a large dispersionof Si, Al and Ca contents, suggesting the use of different starting raw materials. The most commoncrystalline phases used as opacifiers and colorants are quartz and wollastonite. Crystalline aggregates ofSnO2 are present in the gray cakes, whereas PbSnO3 crystals are found in two green mosaic tesserae. Allthe red samples contain small clusters of metallic copper. On the basis of the chemical composition, it ispossible to confirm that most of the samples were produced in the XIII–XIV century, while no specificconclusions were reached on the possible use of the glass cakes as raw glass materials for the productionof the investigated mosaic tesserae.