Archaeometry of a group of chalcolithic ceramics from Bursa-aktopraklik höyük

In this study, 15 unclassified ceramic fragments from the Chalcolithic period, unearthed at Aktopraklık Höyük in Bursa province, were characterized through archaeometric analyses. Chemical compositions of the samples were determined using X-Ray Fluorescence (XRF), while mineralogical analyses were conducted via X-Ray Diffraction (XRD). Petrographic examinations were performed on thin sections using Optical Microscopy (OM), and microstructural and microchemical features were investigated using Scanning Electron Microscopy (SEM). Additionally, Energy Dispersive Spectroscopy (EDS) was employed to analyze the microchemical composition of specific points or areas on the samples. The surface compositions of organic and inorganic compounds were further characterized using Raman Spectroscopy. These analyses enabled the evaluation of ceramic production technology in terms of forming techniques, raw materials used, firing temperature and atmosphere, firing conditions, porosity, grain size, texture, homogeneity, and color. According to XRD results, the presence of high-temperature phases such as spinel, anorthite, and diopside indicates firing temperatures in the range of 900°C to 1000°C. The simultaneous presence of hematite and magnetite phases suggests that the ceramics were fired in a mixed (reducing-oxidizing) atmosphere. The coexistence of these high-temperature phases and iron oxides implies that the production was carried out in a controlled environment, where both heat and kiln atmosphere were regulated. Microstructural images obtained via SEM revealed a high degree of vitrification in the samples. Optical microscopy data showed that the potters incorporated quartz, plagioclase, biotite, muscovite, metamorphic rock fragments, calcite, and grog (crushed fired ceramic) into the clay matrix to enhance thermal shock resistance, melting behavior, and mechanical strength. Chemical and petrographic analyses indicate that local raw materials were preferred in production. The presence of rock fragments such as quartz and calcite with heterogeneous grain sizes and distributions in the matrix suggests that the clays were used without any sieving process. Furthermore, petrographic analyses imply that the clay recipes were tailored according to the intended function of the vessels, and that production may have taken place in multiple workshops.