A provenance study of lapis lazuli

Lapis Lazuli is one of the oldest precious stone, being used as early as 7000 years ago : jewels, amulets and vases are examples of objects produced using this material. Only few sources exist in the world due to the low probability of geological conditions in which lapis lazuli can be formed. Since art objects produced using this material are valuables, only non destructive investigations can be carried out to identify the provenance of the raw materials. A systematic study was performed on 15 semi-thin sections of lapis lazuli coming from 4 different quarries using a multi-technique approach (cold-CL, SEM- EDS-CL and micro-Raman) to univocally identify some markers (trace elements, peculiar phases, luminescence). This characterisation was propaedeutic for Ion Beam Analysis (IL/PIXE/PIGE measurements), because they can be performed in air and on big samples and we’ve already proved that we can identify the same markers also with IBA. Even though this study has been done on rocks (aggregate of different minerals), some of the results concern the lazurite, the main mineral of the ultramarine blue, a very precious pigment. Further studies may be focused on pigments and we think we can extend some of the markers we’ve already found for rocks also to pigments, in order to find out a way to distinguish the provenance of the raw materials employed for the paintings.