Historical mortars beyond Pompeii: the example of Villa del Pezzolo (Sorrento Peninsula)

Villa del Pezzolo is an example of a Roman villa located in the Bay of Naples, which includes several worldwide known archaeological sites, among which Pompeii represents, by far, an almost unique example of a still-visible ancient town. Nevertheless, minor, but not for importance, sites (villas, cisterns, thermae, necropolis, etc.) are widespread all over the Bay of Naples.Goal of this study is the archaeometric characterisation of the lime-based mortars from Villa del Pezzolo, a Roman villa dated from the 1st century B.C. to 3rd century A.D. Villa del Pezzolo is located in Marina di Equa (modern Seiano) in southern Italy. This patrician Roman Villa is very interesting for both archaeologists and geologists because represents one site, along Sorrento Peninsula coast, where the consequences of the A.D. 79 eruption of Mt. Vesuvius are clearly visible, despite the great distance from the eruptive center. Sampling was designed by gathering all the available information about geology and archaeological history of the site in strict cooperation with the archaeologists from the Superintendence of Archaeological Heritage of Campania, who recognised three building phases of the monument. Therefore, representative and non-invasive samples of each of the three building phases, were collected. A multi-analytical mineralogical-petrographic approach was implemented for the investigation by means of PLM, XRPD, SEM–EDS, TG/DTA, and MIP. The analyses of mortars from Villa del Pezzolo evidenced the use of local geomaterials composed by sedimentary calcareous and volcanic aggregates, but also con rmed the three distinct building phases identi ed by archaeologists. Volcanic tuff fragments identi ed in mortars of the 1st building phase are ascribed to the Campanian Ignimbrite formation, widely cropping out in the Sorrento Peninsula. This was con rmed by the presence of glassy shards, partially devitri ed and replaced by authigenic feldspar: a typical feature of welded gray Campanian Ignimbrite lithofacies (WGI; Langella et al., 2013). The volcanic aggregates in samples of the 2nd and 3rd building phases show, instead, the presence of leucite-bearing volcanic scoriae and garnet crystals, which are related to the Somma-Vesuvius activity. The study of these mortars allowed us to: 1) understand the different production technologies, 2) highlight the use of materials with hydraulic behaviour, such as pozzolanic materials and ctile fragments, 3) con rm the three building phases from compositional features of mortars and 4) highlight the change over time of the supply area of the volcanic aggregate for mortar mix-design.