Characterisation of lapis lazuli for a provenance study by means of SEM-EDX and SEM-cathodoluminescence

Abstract

Lapis lazuli has been used for more than 7000 years for the manufacture of precious objects and jewels. The main quarry for this stone is still active in Afghanistan (Badakhshan), but there are other quarries that could have been exploited since antiquity. Sources that have been suggested in previous works are: Pamir mountains (Lyadzhuar Dara, Tajikistan), Pakistan (Chagai Hills), Siberia (Irkutsk, near Lake Baikal), Iran and Sinai. The last two possibilities are not geologically confirmed and their interpretations are still debated. For this reason a provenance study of lapis lazuli could provide answers to some important issues. In particular it is possible to study in depth the use and the dissemination of this rock through historic commercial routes. 
 In the present work a systematic study has been performed on lapis lazuli from four quarries (Afghanistan, Chile, Siberia and Tajikistan) using Energy Dispersive X-ray spectroscopy (EDX) and cathodoluminescence (CL) coupled with a SEM. The main goal of this characterisation is to find at least one marker for each provenance: these markers could be the presence or the absence of a mineralogical phase, or one or more elements present in a peculiar mineral, or the different luminescence of the same mineral.