X-ray fluorescence determination using glass bead samples and synthetic calibration standards for reliable routine analyses of ancient pottery

Abstract

An X-ray fluorescence determination technique using glass bead samples with 1 : 10 sample-to-flux ratios was developed for the reliable and routine analysis of silicic archaeological and geochemical samples (e.g., pottery, clay, rock, and soil) in order to estimate provenance. Synthetic calibration standards were prepared by compounding chemical reagents (oxides, carbonates, and diphosphate) to construct calibration curves for 22 components (Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, K₂O, CaO, TiO₂, MnO, Fe₂O₃, V, Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, and Pb). The standards were produced by imitation of the chemical compositions of Japanese pottery. The calibration curves showed good linearity with correlation coefficients greater than 0.997. The method was validated by assaying three geochemical reference materials. Considering the uncertainty that was estimated from the difference between the analytical and recommended values and the standard deviation of the measurement, the analytical results were in good agreement with the recommended values. The new method produced much more accurate results than those obtained by semi-fundamental parameter calculation using software installed on the XRF spectrometer. The proposed method was used to determine 22 components in 20 Jomon pottery samples and 10 clay samples excavated from the Nakatai site in Japan. The reliable chemical composition data revealed information about the pottery's origin, including the type of raw clay used and the provenance.