Simple Methods for Quantitative X-Ray Fluorescence Analysis of Ancient Metal Objects of Archaeological Interest

In quantitative EDXRF analysis of ancient metallic objects two main difficulties arise: i) how to find out the correction factors for the irregular shape or relief effects and ii) how to measure the true composition of the bulk metal under the surface patina. In the case of coins, taken as a typical example, point i) could, in principle, be by-passed by casting pure metal copies of specimens and comparing XRF intensities with the ones from regularly shaped standards. The interest in examining coins, however, mostly depends on the possibility of the analysis method to be applied to several pieces and XRF analysis should prove to be unpractical in this case. In general we have been looking for methods which are non destructive, simple, cheap, with no consequent effect and possibly apt to in-situ measurements by portable instruments. Gold alloy objects do not normally present a patina on the surface so, by choosing proper geometric conditions during irradiation and by resorting to XRF line intensity ratios, it is possible to get rid of the problem of evaluating geometric factors.