The San Giovanni Baptistery in Florence (Italy): characterisation of the serpentinite floor

The San Giovanni Baptistery in Florence (Italy) is an outstanding worldwide monument, representative of Romanesque architecture, dating back at least to the XII century. The whole edifice is externally revetted by white marble of different provenance and, subordinately, of serpentinite, commercially known as "green marble". This latter is a rock formed from the transformation of ultramafic rocks during low-grade metamorphism or hydrothermal processes; it has been used for building and ornamental purposes since ancient times. In the San Giovanni Baptistery, in addition to the facade, the "green marble" was used on the floor, which consists of white and green tarsias forming an oriental motif. In this work, we studied, through a multi-analytical approach, the green tarsias to compositionally characterise the Baptistery's floor. At the same time, serpentinite samples from different ancient Tuscany quarries were collected and studied to compare their characteristics with those of the "green marble" from Baptistery floor.