From the Pyrenees to the Alps: Evidence of the use of aerinite on XII century fresco paintings at Novalesa abbey (Piemonte)

The chemical analysis of paintings is a powerful source of information when aiming to find relationships among different cultures or geographical areas. Indeed, the presence of particular colourants, specific of one area or of one pictorial school, could indicate that artists coming from abroad were at work outside of their usual boundaries, or that pigments were imported from markets located at great distance. The case of a turquoise pigment found on a 12th century mural painting at the abbey of Novalesa (Piemonte, North-western Italy) is an example of what, according to the authors, should be seen as an example of travelling workers. Analytical evidences given by in situ XRF and FORS and by micro-invasive Raman, XRD and SEM-EDX measurements allowed identifying the rare pigment aerinite, an iron silicate extracted in the Pyrenees and only known to have been used in the medieval area comprising the Pyrenees and south-western France. Not only was its presence previously unreported in Italy, but even the layering of the pictorial layers was unusual. The aerinite layer lies under a thin, translucent layer of gypsum, which was perhaps applied in order to tune its hue and enhance the contrast with the more precious lapis lazuli also found in the mural painting. This unusual but significant identification strongly suggests that foreign painters coming from Pyrenees could have worked at Novalesa abbey in 12th century, reversing the previous hypotheses of a local production based on iconographic studies.