Characterization of ancient ceramic using micro-Raman spectroscopy: the cases of Motya (Italy) and Khirbet al-Batrawy (Jordan)

In the last years, the number of scientific contributions in which Raman spectroscopy is the key technique to analyse archaeological objects is continuously increasing. In particular, the application of this non-destructive technique in the characterization of ancient ceramic has received a major boost. The spectroscopic information obtained by Raman analysis allows for the mineralogical characterization of pottery, answering to the main questions of archaeologists about the nature and provenance of raw materials for ceramic production, as well as exploring the technological aspects of the firing conditions and post-burial processes.[1-8] We report in this study two different types of ceramics in terms of technological fingerprints and preparation of the raw materials with the aim to show how micro-Raman spectroscopy can answer the above questions. Micro-Raman spectroscopy has been applied on ancient ceramics from two archaeological sites of the Mediterranean area and Near East. The first case is Punic “Black-Gloss Ware” from the Phoenician-Punic site of Motya (Sicily, Italy), dating back from the end of 6th to the early 4th century B.C. These ceramics are the result of a high technological background due to imitation of the most famous Attic production, diffused in all Mediterranean world. As a second case study, pottery samples with lower technological background have been selected from the archaeological site of Khirbet al-Batrawy (Jordan), dating back in the III millennium B.C. The use of micro-Raman spectroscopy allowed us to characterize the mineralogical composition of the vessels fragments in order to define the pottery composition and the firing conditions, the nature of the black gloss of Motyan ceramics and of the superficial decorations of Jordan ceramic. Moreover, Raman results combined with those obtained by optical microscopy, X-ray diffraction and SEM-EDAX analysis helped in the reconstruction of the raw material provenance. In the case of Motya samples, the internal body is composed by quartz, feldspars, pyroxenes, micas, gehlenite, magnetite, and haematite. In addition to previous minerals hercynite also occurs in the black gloss. Chemical data showed that the main body and the black gloss contained the same major elements: Si, Al, Fe, Ca, K, Mg, Ti, and Na. However, a Fe-enrichment in the black gloss has been observed. The ceramic samples were exposed to similar firing temperatures and fO2 as suggested by mineral assemblage: estimated T is the range 1000-1100 °C at oxidizing-reducing-oxidizing conditions. The potential sources of raw materials used for ceramic production are difficult to infer as the starting material was selected and purified; however, the presence of a kiln in Motya proves a local production.[9] In the Khirbet al-Batrawy pottery, calcite and quartz are the main components. Hematite, magnetite and carbon are frequently found in all samples. K-feldspar, plagioclase, apatite, gypsum, titanium dioxide (anatase and rutile), pyroxenes, bassanite, barite, zircon, and olivine have been detected in minor amounts and only in few samples. Detailed micro-Raman analysis has been carried out on the superficial decorations of fragments. Raman spectra revealed the occurrence of hematite in red decorations, whereas amorphous carbon has been found in the black ones. The co-presence of calcite, diopside, anatase, and rutile, mineral phases having different thermal fields of stability, allows to hypothesize a firing temperature range of Khirbet al-Batrawy ceramic between 850 and 900 °C. The diffuse occurrence of hematite probably indicates an oxidizing atmosphere during firing, whereas the presence of magnetite could indicate an incomplete transformation from magnetite to hematite.[10] The exhaustive information about mineralogical composition in potteries obtained allows to define the technological process of production, underlining the key role of micro Raman spectroscopy in the study of archaeological ceramic. Figure 1. Views of the two archaeological sites: Motya (a) and Khirbet al-Batrawy (b). References [1] G. Barone, S. Ioppolo, D. Majolino, P. Migliardo, G. Tigano, J. Cult. Herit. 2002, 3,145. [2] C.M. Belfiore, M. di Bella, M. Triscari, M. Viccaro, Mater. charact. 2010, 62, 440. [3] G. Cultrone, C. Rodriguez-Navarro, E. Sebastian, O. Cazalla, M.J. De La Torre, Eur. J. Mineral. 2001, 13, 621. [4] A. Iordanidis, J. Garcia-Guinea, G. Karamitrou-Mentessidi, Mater. Charact. 2009, 60, 292. [5] L. Maritan, Eur. J. Mineral. 2004, 16, 297. [6] C. Rathossi, P. Tsolis-Katagas, C. Katagas, Appl Clay Sci, 2004, 24, 313. [7] C. Tschegg, J. Archeol. Sci. 2009, 36, 2155. [8] G. Velraj, K. Janaki, A.M. Musthafa, R. Palanivel, Appl. Clay Sci. 2009, 43, 303. [9] G. Falsone, Struttura e origine orientale dei forni del vasaio di Mozia, Fondazione G. Whitaker, Palermo, 1981, p.89. [10] C. Lofrumento, A. Zoppi, E.M. Castellucci, J. Raman Spectrosc. 2004, 35, 650.