Abstract The most frequently used material in Florentine Renaissance architecture was Pietra Serena, a sandstone that nowadays is found in a quite satisfactory state of conservation. The reason for this is that architects and stone cutters in the past made careful selections of the materials they employed. This conscientious picking out was very important because most sandstone layers have a composition that is not always suitable for assuring an acceptable durability. This paper deals with the mineralogical, chemical, petrographical and physical characteristics of the Pietra Serena sandstone quarried in the hills near Florence in order to verify what was affirmed by Vasari (1568) , Tuscan painter, architect and historian of art of the 16th century, and other Tuscan naturalists regarding the quality of this sandstone. As a matter of fact, analyses demonstrate that the Pietra Serena sandstones quarried in the hills of Settignano (to the northeast of Florence) and in the Gonfolina area (Lastra a Signa, to the west of Florence), are composed of layers particularly rich in calcite present mainly as sparitic cement. This calcitic cement gives great durability to the stone as is demonstrated by the good state of conservation of some Florentine monuments realized with Pietra Serena.

Abstract The paper presents an overview of the principal stone materials used in the historical architecture of Tuscany, a region of central Italy characterized by a great variety of landscapes. The large number of these materials reflects the complex geology of the region, where each village and town has a unique identity conferred by the architecture and typical colours of the construction materials. The urban areas that have developed in the foothills of the Apennines are, characterized by the use of sandstone, while the towns and villages of central-southern Tuscany are generally more heterogeneous, with an abundant use of bricks and travertine. The information presented is focused on the use of the stone materials during the different epochs, their geopetrographical characteristics and their most common durability problems.

Abstract Maastricht limestone is a soft bioclastic calcarenite of the Upper Cretaceous period cropping out in southern Limburg between Belgium and The Netherlands. This material was widely used from the Middle Ages to the Renaissance. Four different varieties can be distinguished according to fossil content and petrographic characteristics, which determine slight differences in compressive strength. Despite its poor mechanical characteristics, the material is very durable with remarkable frost resistance. This is mainly due to the pore dimensions (the most frequent pore radius class is 16–64 µm) but also to the particular kind of weathering that causes the formation of a protective ‘skin’ through a process of dissolution of unstable aragonite from serpulids and calcite precipitation in the pores of the external layer. The physical characteristics and the mechanical properties (using the drilling resistance measurement system (DRMS) method) of the hard layer that developed on the surface of Tongeren Cathedral, constructed using the Sibbe variety of Maastricht limestone, were investigated and compared with those of the quarry material. This comparison made it possible to emphasize the particular hardness of this surface in contrast to the outer layer of the quarry material. Moreover, it was possible to determine its thickness and to infer that this hard layer was formed after only 15 years of exposure.