Determination of the composition of the ancient colour pigments used by artists in Singida and Kondoa-Irangi rock paints by XRF

In central Tanzania there is a large number of ancient rock paintings which have been drawn mostly on shelter rocks. The colours used in the paintings are white, red yellow and black. The pigments and the material used by ancient artist in making these colours were not well known. This study aimed in determining the composition of the colours and suggests the pigments and materials used in making colours. Two independent techniques namely WDXRF and TXRF were used to determine the composition while CHN element analyzer elemental analyzer was used to determine the presence and amount of organic carbon in the samples. Samples used in WDXRF were of two types, paint sample which contain both colour pigment and rock on which the printings were drawn and the rock sample which is the rock only, the results from rock samples were obtained from very soft scratch on paintings in order to obtain only colour was found to be from red ochre (Fe2O3), yellow colour was found to be from either Titanium yellow or yellow ochre (Fe2O3 X nH2O), white colour from chalk (CaCo3) and gypsaum (CaSo4X2o) white colour from Ivory black (C + Ca3(PO4)2). All pigments were found to contain some amount of organic carbon in different concentrations. Organic carbon in the pigment is related to the use of organic binders during preparation of the colours. Furthermore some pigments were found to contain large amount of calcium and phosphorus which suggest the usage of bones preparation of those pigments especially in white and black colours.