The stone tesserae of the mosaics in the “Domus di Orione” at Pompeii: where do they come from? An archaeometric study

This paper presents the results of an archaeometric study of the stone materials from two Pompeian mosaics in the “Domus di Orione” (House of Orion). The study concerns the stone tesserae of the two famous emblemata featuring the story of the Greek hero, found in a house excavated from 2018 to 2020. Initial visual examination of the polychrome stone tesserae identified some typical stones and marbles classically used in Roman times. Macroscopic observation was then completed by an in-depth mineralogical and petrographic analysis of a selected set of 25 stone tesserae, using polarised optical microscopy, X-ray powder diffraction, stable isotopes analysis, and μ-Raman spectroscopy. The comprehensive investigations revealed that the stone mosaic tesserae are made essentially of sedimentary lithotypes, predominantly of Italian origin and, in some cases, likely sourced locally. Furthermore, a very small number of brick tesserae was also found; they were produced from local raw materials, as were the bedding mortars. In all, 13 types of stone were identified, some of which are historically well known, such as litomarga verde, pietra paesina, giallo antico (marmor numidicum), and various types of bigi morati. Overall, the predominantly Italian, and sometimes possibly autochthonous, origin of the materials suggests on-site production of the mosaics.