A Non-Invasive In Situ Spectroscopic Analysis of Cinnabar Minerals to Assist Provenance Studies of Archaeological Pigments

Abstract

This study presents a non-invasive in situ methodology based on the use of portable elemental (energy dispersive X-ray fluorescence spectroscopy, EDXRF) and molecular (Raman spectroscopy) spectroscopic-based instrumentation as a tool to obtain preliminary information to assist subsequent provenance studies of archaeological cinnabar pigments in the laboratory. In this work, six cinnabar mineral ores, extracted from the Almadén mining district and an original raw pigment coming from the Archaeological Park of Pompeii have been analyzed. As the detection capacities and spectral resolution of the portable instruments are usually poorer than the equivalent benchtop equipment, a comparative study of the in-situ and laboratory results was conducted. Afterward, chemometric data treatment was performed considering both the molecular and elemental information. According to the elemental results, it was not possible to find a strong concordance between the cinnabar ores and the pigment from Pompeii, suggesting the need for additional methodologies in the laboratory (isotope ratio analysis) to complete a proper provenance study. However, this approach was useful to classify the ores according to their mineralogical differences. Therefore, this methodology could be proposed as a useful tool to conduct a representative sampling of the cinnabar mineral ores to be considered in a provenance study of archaeological cinnabar pigments.