Characterization of stones used as stowage and ballast in the ships of the ancient San Rossore Harbour (Pisa)

In December 1998 the escavation for the construction of a building near S. Rossore railway station, allowed the discovery of the ancient remains of Pisa Harbour. A thick layer of sand levels includes the remains of the ancient harbour’s structures and 19 wreckages with their load. These findings can be referred to the late Ellenistic - late Ancient age. Among the materials transported by the ships, numerous large rounded stones used for ballast have been found. The provenance of the stone used for the ballast, i.e. for maintenance of a good trim, can furnish important information about the ancient trade-route.   A part of the material analysed comes from specific boats (ellenistic ship, VIII-I sec. B.C; B ship, III-II B.C; D ship, I-V A.D.). Another part, coming from a chaotic layer, cannot be ascribed to a specific ship, but its age is between III sec. B.C and I sec. A.D. The aim of this work is the petrographical characterisation of the ballast stones in order to give information about the possible areas of origin of the rocks themselves. These data could shed light on the routes taken by the ships, although it cannot be ruled out that the materials may have been re-utilised.