The key role of micro-Raman spectroscopy in the study of ancient ceramics: the case of Jordan potteries from the archaeological site of Khirbet al-Batrawy

In this work micro-Raman (μ-Raman) spectroscopy has been used, as a preliminary and non-destructive technique, in order to investigate the mineralogical composition and to define the maximum firing temperature and fO2 of ancient ceramic materials. The studied ceramics come from the archaeological site of Khirbet al-Batrawy (north-central Jordan), dating back to the Early Bronze Age (3000-2000 B.C.). The results highlighted that ceramic body is composed mainly by quartz and calcite, and minor amount of feldspars and hematite. In addition, apatite and zircon, important markers to identify the provenance of raw materials, have been detected. Furthermore, the occurrence of gypsum has been related to both rehydration of anhydrite and burial alteration processes. Micro-Raman spectroscopy was helpful to investigate the nature of the pigments of these ceramics: the red colour was obtained by hematite whereas the dark pigment by amorphous carbon. Mineral assemblage allowed estimating the maximum firing temperature of these pottery vessels between 850 and 950 °C. The results of μ-Raman spectroscopy were then compared to those of X-ray diffraction analysis. The results of this comparison suggest that μ-Raman spectroscopy could have a key role in the study of ceramic materials. Even if this analytical technique cannot replace other traditional methodologies for a complete and coherent pottery analysis, the outcomes here reported suggest that the application of this non-destructive technique could provide significant information on mineralogical composition, resulting a useful tool for the characterization of archaeological ceramic samples for which manipulation and/or consumption are not allowed.