Chemical composition of the clays as indicator raw material sources
The paper deals with investigation of the chemical composition of unglazed pottery from excavations at the Bulgarian settlements as well as clay, selected from present outputs of ceramic raw materials, located near the medieval settlements. The results of the study have revealed significant distinction of major- and trace element composition between the groups of ceramics. The difference of macro-elemental composition is largely determined with the recipe of ceramic biscuit. Thus, the high calcium content consistens with the addition of river shells, high content of silicon -the addition of sand. More interesting picture has been revealed during the study composition of so called “trace elements”. Nine groups of ceramics with various element set have been singled out. The first two groups consist of import ceramics another groups have a rather pronounced set of elements. Chromium, vanadium, and nickel have the greatest variation of the content. The largest variety of trace element composition is observed for clay deposits with different localization, and concentration of Cr, V and Ni in different clay also differs significantly. Thus, the elements-markers, typical for various clays, have been revealed. Comparative analysis of the obtained data for the clay raw materials and for the ceramics has been carried out. Results of the research show the prospects of study the elemental composition in purpose of determining a localization of raw material source for ceramic production.