The use of volcanic stones in architecture: the exemple of Etnean region. An overview

In the Etnean area the relationship between the volcano and the people is very close and from prehistoric times the population have made use of volcanic rocks in many productive activities. In this paper its use in architecture in this part of Eastern Sicily will be examined. At the moment, the extraction activity is quite intense as testify by the presence of 49 quarries of crushed stones and of freestones. The latter is distinguishable by massive and vesciculated types, which are both characterised by very homogeneous petrographic and petrophysical properties. In the past, the use of volcanic materials was very intense during the reconstruction of Catania after the 1693 earthquake such as stones in walls and basements of buildings, as facing for the facades of monuments, frequently alternated with white limestone, or also as a decorative element. Piroclastites, crushed volcanic rocks or soil thermally modified by the lava flows (locally named ghiara) were added to mortars and plasters thereby obtaining different chromatic effects. The volcanic stones used in many monuments and buildings frequently present forms of degradations, the most frequent of which is the formation of chips due to the crystallization of salts.