Preliminary archaeometric investigations on ancient mortars from archaeological site of Velia (Salerno, Southern Italy)

Elea-Velia is an important Greek colony of Magna Graecia, founded by the inhabitants of Phocaea (Turkey), in the last quarter of the sixth century BC. The town, known for the Philosophical School of Parmenides and Zeno, develops considerably between the Classical and Hellenistic age, preserving, in Roman period, an important role in the medium and lower Tyrrhenian sea. The Masseria Cobellis building, recently investigated by this research team, is one of the most interesting examples of public architecture during the Roman period of the town. This complex is built on the site of a natural spring. It presents in its last phase of construction, dating to the end of the first century AD, a large rectangular open area, bordered by porticoes, with a nymphaeum and an aula in axial and highlighted position. The building seems to rework some models also popular in Campania during the early Imperial age, pointing features of the local architectural repertoires and the new élites’ needs. The building, whose interpretation is still debated, could have a religious character, due to the presence of natural spring, but it is not ruled out a link with the cult of the Imperial Family. The complex shows construction techniques in different phases of its building, that may indicate the activity of different workers. As a matter of fact, for other buildings of Velia (Insula II) it has been suggested the presence of workers from Campania. Then the sampling of the mortar was initiated on masonry structures of the various construction phases to analyze the building site organization and verify the use of different binders. It is worth noting that mortars may supply with important information on the constructive history of ancient stony buildings, as well as on local raw materials used to make them. Mortar samples were investigated by means of XRD, SEM-EDS, OM, XRF and TGA techniques. Macroscopically, mortars vary in color from light gray, to creamy white and to light yellow; they can be friable to very hard. Preliminary mineralogical and petrographic characterization show that the Velia mortars can be subdivided into two groups, i.e. the calcite-bearing and the calcite-free samples. Mortars of the first group are composed by a mixture of variable amounts of quartz, K-feldspar, micas, illite and likely analcime. In the calcite-bearing samples, calcium carbonate occurs together with quartz, K-feldspar, Na-feldspar, illite, micas, and locally trace of gypsum, kaolinite, clinopyroxene, and likely philliphsite. Observation under polarized optical microscopy provided information about the various types of components forming the aggregates and the porosity of the investigated samples. Clues for provenance studies, also extended to probable limestone caves used for the preparation of mortars components, will also be discussed.