Validation with Raman spectroscopy of lapis lazuli provenance study

Lapis lazuli is a stone appreciated in the art world since ancient times; its use dates back to more than 6500 years ago. There are few mineral sources of this stone in the world and the provenance characterization is an open question. However, the rarity of the sources certainly represents a positive aspect for the indication of the origin of artefacts. Lapis lazuli is a rock consisting mainly of lazurite, diopside, calcite and pyrite; other constituents may be present, linked to the different mines. In this work, we present the development of a method for the recognition of the sources of lapis lazuli. The results obtained on stones from five samples of known origin and on three sets of unknown polished stones were obtained with Raman analysis. We thus verified the results achieved by our previous assignment based on the use of the synergy between the characteristic fluorescence of X-rays and the luminescence stimulated by X-rays. The choice of using Raman spectroscopy as a fast, non-invasive and portable method to determine the geological provenance of lapis lazuli pigments will then be discussed. Finally, we were able to obtain a clearer distinction for the different classified provenances.