Since pottery, in all its shapes, has always followed through man’s life, today the study of ceramic fragments found during excavations is, to an archaeologist, the key point of a careful historical reconstruction, useful to provide knowledge, which otherwise would have gone lost.

Each artifact of historical, archaeological and artistic interest contains, in fact, hidden information about its origin and its history, that can’t be entirely learned only through the senses, needing instead an interdiscipli- nary approach (Rehren & Pernicka, 2008; Moropoulon & Polikreti, 2009) . In particular, the use of structural and compositional analysis allows to study in detail the chemical composition of the artifacts and to achieve knowledge about the identity and origin of the raw materials, in some cases corresponding to their areas of production (Romich & Weinmann, 2000; Faella et al., 2012) , and to increase our understanding of the eco- nomic-political organization and of the cultural changes of an ancient people (Grave et al., 2008; Grave et al., 2009; Bong et al., 2010) . These data may help to assess, where possible, the extent of the trade and/or the exchange of artifacts among cultural groups, including information on their technological capabilities and development, their work and life conditions, social differentiations and on the functional purposes of the products.

This methodological approach was used in the present study for the analysis of eighty pottery fragments found in Mersin-Yumuktepe (Southern Turkey) and Arslantepe (Malatya, Eastern Turkey), which cover a time span that ranges from the Chalcolithic period (5000 BC ca.) to the Late Bronze Age (1650 - 1200 BC ca.). Besides, both Anatolians sites, at a given time of their existence, were part of a common cultural-political framework that during the Late Bronze Age saw the expansion of the Hittite civilization in these territories (Ertem & Demirci, 1999; Angle et al., 2002; Glatz, 2009) .

Given that the use of non-destructive techniques is fundamentally important for archaeologists and, in general, for an archaeometric study (Bonissoni & Ricci Bitti, 1988; Amelinckx et al., 1997; Ciliberto & Spoto, 2000; Poupeau et al., 2010) , in this chemical-physical and morphological analysis of the ceramics a central role has been given to a non-destructive analytical technique-the scanning electron microscopy-equipped with a system of energy dispersive X-ray spectroscopy (SEM-EDX).

The experimental results obtained have been later processed by using multivariate statistical techniques (Baxter, 1994; Frank & Todeschini, 1994; Baxter, 1995; Lomiento, 2004; Varmuza & Filzmoser, 2009) , such as the Principal Component Analysis (PCA), in order to identify any similarities and/or differences among the analyzed samples; starting from an exhaustive list of chemical-physical data specific to each sample, we also focused on an integrated interpretation, consistent with an archaeological study. Finally, the statistical data processing has allowed the comparison between the material culture of two realities, geographically far away, but culturally close to each other.

The scanning electron microscopy has enabled a morphological and compositional analysis of the internal and external surfaces and of the sections of the eighty samples analyzed. Figure 2 and Figure 3 show two typical SEM images, respectively of the surface (sample n. 11 Arslantepe LB) and of the section (sample n. 4 Arslantepe LB) of the pottery object of this study.

The morphological analysis has allowed to obtain a complete examination of the grain size of the ceramic bodies and, in addition, the identification of the shape and the composition of the present inclusions such as, for

example, crystallites of various nature. Table 1 summarizes main inclusions highlighted in the analyzed sam- ples.

Overall, in the samples, it has been revealed a hiatal granulometry (with granulometric phases of various sizes) consisting of a basic binder phase with fine grain. In particular, it has a clayey material to which has been added a temper fraction coarser and in variable quantities, consisting of sand, inclusions and fossil of several origins.

Table 2 summarizes the semi-quantitative values of the concentration (% w/w) of Na₂O, MgO, Al₂O₃, SiO₂, SO₃, K₂O, CaO, TiO₂, MnO and Fe₂O₃ for each sample, the results of which are reported as normalized% oxides. Each value represents the average of five measurements obtained by using the EDX analysis performed on the

internal section of each sample.

Although the results show a substantial homogeneity among different samples, it is possible to highlight a difference between the two pottery productions. The mean value of the concentration of Na₂O, MgO, Al₂O₃, SiO₂, SO₃, K₂O, CaO, TiO₂, MnO and Fe₂O₃ are equal respectively to 2.23% ± 1.09%, 4.93% ± 1.25%, 12.61% ± 3.05%, 46.24% ± 6.24%, 0.83% ± 1.83%, 3.34% ± 0.70%, 21.08% ± 8.68%, 0.66% ± 0.25%, 0.25% ± 0.21% and 7.73% ± 1.86%. Therefore, for each sample, silicon, calcium, aluminum and iron are majority elements, while titanium, manganese, potassium, sulfur, magnesium and sodium are minority elements and/or trace ele- ments.

The average concentrations of the oxides, determined on the internal section of each ceramic object, were further processed by using the multivariate statistical method of the Principal Component Analysis (PCA). For this purpose we used a matrix consisting of eighty cases (analyzed samples) and ten variables (determined oxides) and the first four main components have been extracted, obtaining a coverage of the total variance equal to 75%.

Figure 4 shows the loading of variables on the first two main components, which separate the concentrations of the oxides along the two factors (Factor 1 and Factor 2). The graph allows discriminating the concentration of oxides detected, more specifically SiO₂ and Al₂O₃ have negative values of the first principal component, while CaO and SO₃ have positive values of it. MnO has negative values on the second principal component, while Na₂O has positive values on the second principal component.

Figure 5 summarizes the results obtained with the PCA method and it allows making some important consid- erations.

Firstly, it is possible to demonstrate among the analyzed findings, a difference between the two pottery productions: in fact, all the samples of Arslantepe except three (n. 2, n. 21 and n. 27 Arslantepe LB) have positive values on the PC2, while the samples from Mersin-Yumuktepe have almost all (45 out of 62 ceramics, approximately 73%) negative values on the same component. Seventeen ceramics from Mersin-Yumuktepe, instead, have a positive value on the PC2 and they overlap with the group of Arslantepe.

The percentages of the oxides detected, therefore, let us infer that the material used for the manufacturing of the finds from Mersin-Yumuktepe have a common origin, as well as substantially common seems to be also the

origin of the raw material used for the production of the finds of Arsalentepe. However, these two types of material are different from each other.

An important element is then given by samples n. 8 and n. 23 (Arslantepe LB) which significantly deviate by the general trend for higher concentrations of CaO, the first, and especially of SO₃, the latter. The same appliesalso to samples n. 15 (Mersin LB 2008), n. 21 (Arslantepe LB) and n. 6 (Mersin C 2009), which have higher average concentration of CaO and MnO, but scarce of SiO₂. The samples n. 1 and n. 12 (Arslantepe LB) have, instead, high concentration of SiO₂ and Al₂O₃, but low concentration of CaO, while the samples n. 9 (Arslantepe LB), n. 9 (Mersin C 2012) and n. 13 (Arslantepe LB) show, respectively, the highest average concentration of Na₂O and Fe₂O₃ (the first two) and of Fe₂O₃ compared to the rest of the finds analyzed. This can be substantially attributed to the use of clays from different sources, which let us assume a non-local production of some of these ceramics.

Nonetheless, our hypothesis must consider that the various qualitative and quantitative composition of pottery mixture may respond to different uses of the finished products. Overall, the differences observed in the ceramic mixture take into account the heterogeneity of the considered context.

The maximum output to this work is given, however, only by the results of the samples of Mersin-Yumuktepe. In fact, almost all samples from the latter show values that fall within −1 and 1 of the PC1 and PC2. This indi- cates a considerable homogeneity from the compositional point of view of the pottery production. The popula- tion of Mersin, in fact, from the Chalcolithic period (5000 BC ca.) until the Late Bronze Age (1650-1200 BC ca.) and, therefore, for more than 3500 years, has allegedly used the same techniques and the same raw materials for the realization of pottery.

This observation probably indicates the use of the same technology for firing the pottery, but this does not prove that all materials investigated were produced by the same furnace.

The archaeometric method used in this work has allowed us to learn important information on the morphology, particle size and chemical composition of the studied ceramic objects.

The simultaneous use of non-destructive techniques, relatively quick and inexpensive, and the subsequent statistical processing of the experimental results obtained made it possible to suggest some important assessments and to highlight some key elements, such as the difference between the pottery production of Mersin-Yumuk- tepe and Arslantepe and the probable millenary productive continuity only of the pottery of Mersin-Yumuktepe. This result is fundamental in the determination of a historical/archaeological framework of these two sites.

The methodology followed in this study can certainly be applied to other archaeological contexts and to other artifacts of historic and artistic interest such as, for instance, glass, sediments and coins.