Multitechnique characterization of lapis lazuli for provenance study by means of ionoluminescence

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. Ionoluminescence (IL) combined with PIXE/PIGE is a good candidate for this task. Similar to cathodoluminescence (CL), IL consists in the collection of luminescence spectra induced by MeV ion (usually protons) irradiation. Advantages of IL are the possibility to work in air on art works and the contemporaneous PIXE/PIGE analysis. The IL capability to distinguish Chilean Lapis Lazuli from Afghan has been demonstrated in a previous paper. In the present work a systematic study was performed on Lapis Lazuli from different quarries using a multi-technique approach (SEM-CL, micro- Raman and SEM-EDS) to univocally identify and characterize luminescent phases. This characterisation was propaedeutic for IL/PIXE/PIGE measurements.