The local black limestones used to make the typical black-and-white alternation of the Pisa’s Romanesque Style

This paper documents the chemical, mineralogical and petrographic characteristics, and some physical properties of the black limestones that were exploited in the Middle Ages for building the Pisa’s monumental architecture. The black limestones are worthy of particular importance in the medieval Pisa’s constructions because they are used to build important buildings (S. Maria Assunta Cathedral, Leaning Tower, Baptistery and several other city churches) and, in particular, the typical black layers that characterize the Pisan architecture are almost always made with these stones. The main local black limestones used as building stones in Pisa belong to the Tuscan Nappe Unit: the Calcare a Rhaetavicula contorta formation, including the black limestone Portoro, outcropping in the Monte Pisano area, and the Calcare selcifero della Val di Lima formation, outcropping in the Monti d’Oltre Serchio area.