The ornamental stones of the Roman thermal baths of Teate Marrucinorum (Chieti, Italy): autoptic, geochemical and minero-petrographic multi-analytical characterisations

Ancient Romans exploited aesthetic natural stones from many sites across their Empire around the Mediterranean, transporting them for thousands of kilometres, to decorate their buildings. Petrographically, these metamorphic, sedimentary and igneous rocks display considerable differences, ranging from simple white stones to vividly coloured lithotypes. The source Region of these coloured stones is typically reconstructed from autoptic (visual and comparative examination of macroscopic or hand-sample scale) determinations, also tacking advantage from the personal expertise of some specialists of the sector.Here, the ornamental stones of the 2nd-century A.D. thermal baths of Teate Marrucinorum (Chieti, Abruzzo region, Italy) are considered and investigated by different and complementary methods. According to their autoptic features or mesoscopic textures, the initial 56 samples were divided into three categories: polychrome stones, grey-striped and white crystalline marbles. These rocks were analysed via bulk autoptic, mineralogical (XRPD) and geochemical (XRF) methods; also, representative thin sections were used for transmission optical microscope (TOM) petrographic and micro-Raman determinations. The δ¹⁸O and δ¹³C isotopic signatures were also characterised for white and grey-striped marbles.The complementary and multi-analytical approach unveils that the grey-striped marble is Greco Scritto , the white marbles come from Carrara ( Marmor Lunense ) and Marmara Island ( Marmor Proconnesium ) sources, whilst the four polychrome stones correspond to Pavonazzetto Antico (Marmor Phrygium ), Cipollino Verde ( Marmor Carystium ), Portasanta ( Marmor Chium ) and Breccia di Settebasi ( Marmor Scyreticum ). The coupling of qualitative observations with quantitative measurements further constrains the provenance and features of aesthetic rocks employed in the ancient town by the Romans.