User: Laura Guidorzi
Organisation: Istituto Nazionale di Fisica Nucleare, Torino
Technique requested: Particle-induced X-ray emission (PIXE)
Facility: AGLAE, the Grand Louvre Accelerator for Elemental Analysis
A systematic study of lapis lazuli provenance has been carried out by our group since 2007, comparing the physical- chemical properties of rocks and historical objects. Lapis lazuli is a semi-precious blue stone which was in fact widely used since antiquity, but its trade in ancient times and the quarries exploited by different civilisations are, at present, still not entirely known.
Ion Beam Analysis was chosen as the principal technique for our measurements due to its non-invasiveness and its possibility to investigate single crystals of specific mineral phases among all the ones constituting this stone. The microbeam line at NewAGLAE is the optimal solution for our scopes, as it works with an extracted beam that allows to analyse also those artefacts that are too precious to be measured in vacuum, granting at the same time very low detection limits thanks to its advanced setup.
During our measurements within the SIBILLA project we were able to analyse in 5 days 17 archaeological samples, retrieved from two different sites in Kerman Province, Iran, supposedly belonging to the Jiroft culture (III millennium BCE). Moreover, it was possible to start some test measurements on 3 small lapis lazuli beads, particularly precious as they come from the Royal Cemetery of Ur (Iraq, III millennium BCE).
Preliminary results have been focused on the analysis of μ-IBIL spectra and for the majority of the samples a weaker marker for Afghan provenance (the 770 nm band) was found. Further data analysis is ongoing and it will be decisive for a definitive provenance attribution to these samples.