EDXRF analysis of metal artefacts from the grave goods of the Royal Tomb 14 of Sipán, Peru

Several metallic sheets (about 1 mm thick) from the grave goods of the Royal Tomb 14 (Sipán, Peru) were characterised by energy dispersive X-ray fluorescence analysis, using both a portable instrument and a capillary collimated spectrometer to investigate details, and micro-Raman spectroscopy. The samples, belonging to the clothing of the warrior priest, resulted composed of thin copper sheets or tumbaga (natural alloy of copper, silver and gold). They were unearthed covered with typical green patina, formed during their long burial and characterised mainly by copper minerals, such as malachite, atacamite and magnetite identified with micro-Raman spectroscopy. Due to deterioration of the original alloy, the artefacts analyzed in this work were rather fragile and could not resist hard polishing aimed at cleaning off corrosion products. So a non-destructive qualitative EDXRF analysis was performed to identify the elemental composition of the metal alloy and a quantitative estimation was made applying the fundamental parameter method. The presence of superficial patina layer and the non-homogeneous composition was also taken into account during calculation. The data obtained, compared to published results from several artefacts found in the nearby tombs, have been treated with a hierarchical statistic analysis.