The stone materials in the cultural heritage: causes of decay and Italian examples

Stones are natural materials that man has always used for the realization of monuments, selecting them in function of various characteristics as availability, workability, chromatic aspect. Often, however, the durability of the stone materials, frequently in antithesis with their workability, is not considered. A rock is a mono or poly-mineral aggregate formed naturally with long and complex processes which result in the lithification. After its formation, it undergoes further transformations that are part of the so-called geochemical cycle. As a matter of fact, each stone is in equilibrium with the environment in which it is located. If the environmental parameters change in time, this causes a loss of the equilibrium and the need of adaptation.