Characterisation of fine wall and eggshell Roman pottery by Raman spectroscopy

Roman pottery from the Oiasso harbour (nowadays Irun, Basque Country) was thoroughly studied by micro-Raman spectroscopy and X-ray diffraction (XRD) analysis in order to identify and characterise the mineralogical composition of those samples and to get a deeper insight into the technologies involved in the elaboration of the ceramic artefacts. The diffraction pattern of the ceramic body shows the presence of mullite and trydimite, which suggests firing temperatures above 1100 degrees C, and alumina-rich raw materials. Additionally, the presence of pseudowollastonite and diopside observed by the XRD and Raman spectroscopy is explained by the high firing temperatures of lime-rich raw materials. Raman microscopy has also provided further information about the heating temperature and composition of the raw materials. The presence of rutile instead of anatase also suggests a strong heating process. Moreover, the presence of hematite (alpha-Fe2O3) and maghemite (gamma-Fe2O3) instead of magnetite (Fe3O4) suggests the oxidising conditions during ceramics firing. The comparison of the minerals found in the different Roman potteries with the characteristic mineralogy of the archaeological site suggests the use of raw material coming from different source areas, opening up an interesting discussion about the commercial networks. Copyright (C) 2010 John Wiley & Sons, Ltd.