Pietraforte, the Florentine building material from the Middle age to contemporary architecture

Pietraforte sandstone is the building material of the Medieval Florence (Italy). This was due to the proximity of its quarries to the city, its availability, ease extraction from the quarry face and to the particular characteristics of durability of the stone, suitable for the buildings and monuments cladding. Florence can be defined as a city in Pietraforte, and this makes it necessary its detailed characterization. The paper reports the geological setting of the Pietraforte sandstone, the mineralogical-petrographic characterization, the physical parameters and also a mineralogical method (based on clay minerals association) for the identification of the source quarries of the most important historical buildings. The knowledge of this lithotype allowed to better understand its decay phenomena.