SOLVING AMBIGUITIES AMONG COARSE-GRAINED GREY GRANITE THROUGH NON-DESTRUCTIVE SOURCING TECHNIQUES APPLIED TO ANTIQUITY

Among the quarries used to manufacture granite shafts used in Mediterranean antiquity, besides the classic coarsegrained grey granite of Mons Claudianus, other similar-looking sources have been described: South Corsica, Andalucia and Nicotera (Calabria). How to discriminate between these sources using non-destructive techniques is not well established. Here we present a scheme using, besides visual inspection, magnetic susceptibility and trace element analyses based on portable X-ray fluorescence. To confirm our non-destructive scheme, we also investigate the ability of the strontium isotopic ratio to discriminate between Mons Claudianus and the Corsican sources. Our survey in various countries (Spain, France, Germany, Italy, Tunisia) confirms that use of Mons Claudianus stone, at least in the form of shafts, was mostly restricted to Rome. On the other hand, the Corsican source has been identified in Tarragona, Die, Lyon, Pisa, Rome, Carthage and Uthina. This proves a wider diffusion of this granite than previously thought. Nicotera shafts also appear to have been exported outside of Calabria, to Rome, Arezzo and Pisa. Finally, we surmise that the use of granite shafts from Andalucia remained local.