Provenance of materials employed in the construction of Orvieto Cathedral (Umbria, Italy)

A multivariate analytical approach was carried out in order to characterize travertine and «basaltina» which are the main building stones employed in the construction of Orvieto Cathedral. Results indicate the existence in the monument of three different lithotypes of «basaltina», «finegrained », «coarse-grained» and «very fine-grained» distinguished on the basis of the size of leucite phenocrysts, and three distinct lithotypes of travertine, stromatolitic, phytohermal and detrital, distinguished on a textural basis. The multivariate approach was a powerful tool in checking historical sources on the provenance of the materials. Comparisons between samples from the Cathedral and homologous samples from ancient quarries and zones of excavation revealed a provenance from a quite narrow zone, between Orvieto and Bagnoregio, for all lithotypes. Comparisons, between homologous samples from different zones in the Cathedral shows that the areas of excavation of «basaltina» and travertine did not change with time.