HIGH-PRECISION NONDESTRUCTIVE X-RAY-FLUORESCENCE METHOD APPLICABLE TO ESTABLISHING THE PROVENANCE OF OBSIDIAN ARTIFACTS

A high-precision, non-destructuve x-ray fluorescence (XRF) method has been developed for the determination of both trace and major elements in obsidian archaeological artifacts. Other than brushing the artifact surface clean, no sample preparation is required. The method developed proves XRF to be an extremely valuable technique for the analysis of archaeological obsidian samples which cannot be destroyed or altered because of their importance for historical studies. The method is applicable to both thick and thin samples which have wide variations in size and shapes. The method has been used to establish the provenance of a number of obsidian artifacts. The results ascertained for groups of samples from three provenances are discussed in this paper. The concentrations of thirteen trace (Ti, Mn, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Ba, Pb and Th) and three major (K, Ca and Fe) elements were determined from one x-ray spectrum which was acquired during a 1000 s counting interval. The concentrations of the six most precisely measured elements (Fe, Rb, Sr, Y, Zr and Ba) yielded precisions which averaged 2.3%. The mean concentrations determined for five of these elements (excluding Y) differed on average by only 2.0% from published values which were ascertained by neutron activation analysis and XRF. The average standard deviations realized for the other ten elements determined was ca. 7%.