Mineral and chemical composition of bronze age pottery from the Levoberezhnoe settlement (Sintashta II)

Seventeen pottery samples of the Sintashta, Petrovka, and Mezhovka cultures at the Levoberezhnoe settlement (Sintashta II) in the basin of the Tobol River, discovered in the cultural complexes which were dated by AMS-radiocarbon analysis, were studied using X-ray diffraction and bulk chemical analysis. The research results were compared with technical and technological analysis of the same pottery complex. It has been established that pottery of the Sintashta and Petrovka cultures had similar mineral composition with the later pottery of the Mezhovka culture from the same settlement, although they significantly differed in many interrelated indicators. The Sintashta and Petrovka pottery revealed high content of talc and chlorite which occurred in very small mass fractions and more often were completely absent from the Mezhovka pottery which, in turn, was distinguished by significantly higher content of mica and quartz, and presence of illite and smectite. These diverging features are primarily associated with differences in the composition of fabrics in different cultural and technological traditions, and differentfiring temperatures. In the pottery of the Sintashta culture, minerals of the serpentine group disintegrated, which happens at a temperature of about 600°C, while in the pottery of the Mezhovka culture, illite and smectite have been preserved. The temperature of destruction of the crystalline grid in these minerals is about 600°C. Thus, it is likely thatfiring temperature was above 600°C for the Sintashta pottery and below 600°Cfor the Mezhovka pottery. The use of quantitative criteria makes it possible to identify even small-sized, indistinctive, and scarce pottery evidence with the help of X-ray diffraction, which is of great importance for interpreting archaeological sites.