Minero-petrographic characterisation of roman mosaic tiles from Aquileia

Despite the importance of Romans mosaic of Aquileia, only few works are specifically aimed to their study [1, 2] and there is a strong need to define technology and materials used for their production. In this work, 150 specimens of Roman mosaic tiles (tesserae) are considered. The material under investigation was collected during archaeological field-walking survey of the fields surrounding the center of Aquileia, the capital of the Regio X of the Roman Empire located in NE Italy. Thanks to the large number of selected samples, this research provides a broad study of lithic materials employed for the production of roman mosaic tesserae. Initial optical investigations (colorimetric and optical microscopy analysis) have enabled to cluster the specimens into 6 groups in relation to their colour. This preliminary characterisation has underlined how burial condition have induced changes in colour of the original material. Afterwards, petrographic characterization was performed in order to assess the nature of the rock types used. Thin sections of specimens were analysed by Microscope Polarized Light (PLM), Scanning Electron Microscopy with EDX probe, in order to investigate the morphology, the mineral phase and the chemical composition of the lithic matrix. Comparison of the results obtained from the analysis of the tesserae with the data present in literature revealed important similarities between the materials. These results confirmed the use of sedimentary rocks as reported in literature [3, 4]: limestone from Trieste surroundings and the Karst area. To the best of our knowledge, this research represents the widest characterisation analysis of mosaic tesserae from Aquileia ever performed and provides a clear picture of the technology and materials most used by Romans in Aquileia’s settlement for the production of mosaics. Moreover, our results constitute a relevant step forward in the understanding of the possible provenience of the raw materials.