A multi analytical approach to discriminate the Italian colored marble “Portasanta”from Portasanta “Marmor Chium” (Greece)

The “marble” Portasanta from Caldana (Grosseto, Italy) takes its name from the strict resemblance tothe ancient Marmor Chium (also this called Portasanta) coming from the island of Chios in Greece. Inthis work, a complete characterization of the Italian Portasanta was made: chemical (X-ray fluorescenceand isotopic analyses), mineralogical (X-ray diffraction on the bulk sample and on insoluble residueafter acid attack), physical (water accessible porosity and imbibition coefficients), petrographical (opticalmicroscopy) and mechanical (compressive strength test) analyses have been carried out in order toobtain a better distinction between Italian and Greek “marble”, sometimes mistaken. The Portasanta fromCaldana (Italy) was quarried surely in the sixteenth century, but a possible use of this material duringRoman time is still in doubt. The study of samples from some Tuscan archaeological sites (Torraccia diChiusi, Siena and Roselle, Grosseto) allows us to confirm the use of Portasanta from Chios for the Torracciasite and that of Caldana for Roselle.