Chemical composition of the clays as indicator raw material sources

The paper presents the results of study on the chemical composition of unglazed pottery from the excavations of the Bulgar fortified settlement site and the clay, selected from the modern deposits of ceramic raw materials located near the medieval settlement sites. Significant differences in macro- and microelement composition of different groups of ceramics have been revealed. The difference in the macroelemental composition is largely determined by the ceramic fabric recipe. Thus, the high calcium content corresponds to the addition of river shells, the high content of silicon results from sand addition. A more interesting picture has been revealed in the course of studies of the so-called “trace elements” (microelements). Nine groups of ceramics with different elemental set have been distinguished. The first two groups consist of imported ceramics; other groups have demonstrated a rather pronounced elemental composition. The most notable variations are observed in chromium, vanadium and nickel content. Similar microelement composition variety has been observed in clays from deposits of different localization, while the concentration of the mentioned elements in a variety of clays also differs considerably. Therefore, marker elements typical of different clays have been identified. A comparative analysis of the data obtained for clay raw materials and ceramics has been conducted. The results demonstrate the potential of studying the elemental composition in order to determine the localization of the raw material sources for ceramic production.