Geo-heritage Tour Across the Ornamental Stone of the Historic Centre of Ivrea, UNESCO World Heritage Site (Piedmont region, NW Italy)

Ivrea, the ancient Eporedia founded around 100–101 B.C. by the Romans and UNESCO site from 2018 is a town where stone has always been the most widely used building material, characterizing the architectural identity of the city. In particular, numerous rocks were still visible in the ancient buildings of the historic centre. For this reason, Ivrea was chosen as place on which developing an informative proposal, of geological interest for the conservation of Cultural Heritage. A minero-petrographic study was carried out to identify the different stone materials and their provenance areas used. The origin of rock samples resulted essentially from local or nearby geological units. The most used stones were diorite, tonalite and gabbro and of the Ivrea Verbano Mafic Complex, which crops out in the city of Ivrea itself. Other rocks used were permian granites intruded into the basement of the Serie dei Laghi, syenite and diorite from Oligocenic pluton of Sesia Zone, jadeite orthogneiss and micaschists from the Eclogitic Micaschist Complex of the Sesia Zone; calcschists and Bardiglio Marble from the Piemonte Zone and Serizzo othogneiss from the Antigorio unit of Ossola Valley. In lower quantities, rocks from both extra-regional Italian areas (some carbonate rocks from Southern Alps and the Northern Apennines) and foreign countries (Scandinavian granites) were also used. The data collected were managed through digital systems using geomatics techniques and the results consists of an interactive web site that can be used by a wide audience. It can be visited through any mobile or fixed device at the following link: http://www.geositlab.unito.it/ivrea .The site consists of 13 historical sites of interest in each of which ornamental stones of historical and scientific interest can be observed in detail.