The mural paintings of Ala di Stura (Piedmont, Italy): a hidden treasure investigated

In the small mountain hamlet of Ala di Stura (Piedmont, Lanzo Valleys), a large but relatively unknown artistic heritage is present, made of 110 mural paintings divided among meridians and paintings with religious themes. These artworks are datable among XVI and XXI century. To support the work of touristic promotion carried out by the Commune of Ala di Stura, micro samples have been withdrawn from the most relevant artworks in order to execute Raman and scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) analysis and to have useful information concerning conservation, dating and global knowledge on the artworks themselves that are little known outside Piedmont. Analyses allowed to elucidate phenomena of chromatic alteration (changing of lead pigments), to individuate pigments acting as time markers (synthetic ultramarine blue, arsenical green pigments) and to have information on the origin and exploitation of pictorial materials used by the artists who worked in Ala di Stura. Of particular interest is the fact that all pigments identified in the older paintings, and many among those identified in the newer ones, could be derived from minerals sources present in the Lanzo Valleys, among which is olivenite, a rare copper arsenate used as a green pigment that has rarely cited in the scientific literature.