Pietra da Torre (literally translated from Italian: Tower Stone), taking its name from the wide use made of it to build Siena’s towers. A number of sources confirm that the Pietra da Torre used for Siena’s buildings and monuments came from the nearby Montagnola hills and, in particular, from the western slopes.
It is not easy to describe this material, at least in chromatic terms and without examining geological aspects, given that the definition Pietra da Torre refers to stones from different geological formations. Often described as Calcare Cavernoso - literally translated from Italian: Cave Limestone, it is actually formed by it and its derivatives. A common feature is the “spongy look”; a surface marked by holes sometimes barely visible, some other times few centimetres wide.
The colour of Calcare Cavernoso goes from light to dark grey, with sporadic pigmentations going from red to yellow as well as pink. This material represents only a small portion of the Pietra da Torre used - in the centre of Siena, 25%* - and extracted, although it is difficult to differentiate from its derivatives precisely because of their similar features and the proximity of deposits.
The best known and most popular is the Breccia di Grotti, which we have also used in our kitchen. It is made up almost exclusively of Calcare Cavernoso elements that interact with other fragments from the Montagnola area creating a breccia made up of slightly rounded sediments of different sizes and colours, held together by ochreyellow limestone. This is a rough material that creates heterometric elements of very different sizes, from centimetres to metres, and that at times appears stratified**.