Un primo impiego di serpentinite in un pavimento di graniglia marmorea di una villa rustica romana in Versilia

The excavations of a Villa rustica recently discovered in Pietrasanta (Versilia – Tuscany), at the border of the ancient territory of Luni, made it possible to find out portions of a marble grit flooring with scattered polychrome tesserae dating back to the late republican time. Moreover also some Domus in Luni (Roman town) show the presence of marble grit floorings with polychromes scutulae dating back to the late republican time and the first half of Ist century A.D., testifying a similar cultural background. The structure of the floor consists of a first layer 10 cm thick made of river pebbles (of local provenance) arranged in vertical position according to their main dimension. In the upper part the pebbles are partially included in a ground fired brick mortar few cm thick. This layer is overlaid by a more or less smoothed upper layer made of a marble grit constituted by irregular angular elements of white and grey marble (‘bardiglio’) of a probable Versilian provenance (Seravezza valley) and scattered scutulae of a “green stone”. The petrographical and mineralogical studies allow to suggest that the “green stone” of Villa rustica comes probably from Bracco-Val Graveglia Unit, rather far from Pietrasanta.It could be the result of extraction from the Bracco serpentinites transported along the ancient communication roads or it could come from fluvial pebbles of the Vara river (which flows at Bracco area), feeder of the Magra river, flowing near Luni. The hypothesis of the provenance from the serpentinites outcrops of the Vara valley is possibly linked to intense trades, also of ornamental stone materials, between Luni and the Genoese territory, developed after the conclusion of the Roman-Ligurian wars (155 b.C.) and after the construction of Aemilia Scauri road (the 109 b.C.). The alternative hypothesis of the provenance from pebbles of the river bed better corresponds to the Luni’s tradition of utilizing the available lithological resources in the neighborhood of Roman town.