Fragments of the Western Alpine Chain as Historic Ornamental Stones in Turin (Italy): Enhancement of Urban Geological Heritage through Geotourism

In Piemonte, stone has always been the most widely used raw material for buildings, characterizing the architectural identity of the city of Turin. All kinds of rocks, metamorphic, igneous, and sedimentary, are represented, including gneisses, marbles, granitoids, and, less commonly, limestones. The great variety of ornamental stones is clearly due to the highly composite geological nature of the Piemonte region related to the presence of the orogenic Alpine chain and the sedimentary Tertiary Piemonte Basin. This paper provides a representative list of the most historic ornamental stones of Piemonte, which have been used over the centuries in buildings and architecture. The main stones occurring in Turin have been identified and described from a petrographic and mineralogical point of view in order to find out the corresponding geological units and quarry sites, from which they were exploited. This allows the associated cultural and scientific interest of stones to be emphasized in the architecture of a town which lies between a mountain chain and a hilly region.