Natural ultramarine in the Roman context of Volsinii (Bolsena, Italy): a multianalytical characterization

This study presents a comprehensive analysis of a blue pigment lump discovered near Volsinii (modern Bolsena, Italy), employing ED-XRF, micro-Raman spectroscopy, and XRPD techniques. The pigment was conclusively identified as natural lazurite, the primary component of lapis lazuli. EDXRF analyses, supported by principal component analysis, revealed elemental compositions aligning closely with synthetic ultramarine pigments, yet distinct from Egyptian and Herculaneum blues. Micro-Raman spectroscopy detected characteristic S3⁻ radical peaks at 548 cm-1, with additional shoulders at 585 cm-1 indicative of natural origin. XRPD confirmed a predominantly lazurite crystalline structure, lacking kaolinite impurities typical of synthetic variants. The presence of such a rare and valuable pigment in a provincial Roman context suggests sophisticated material procurement and artistic practices, challenging prevailing assumptions about pigment distribution in antiquity.