Isotope Analysis and Its Applications to the Study of Ancient Indian Glass

The use of lead, strontium and neodymium isotope signatures in ancient glass is developing rapidly and allows the identification of the geological origin of the different raw materials entering the composition of the glass. This approach has been recently applied to glass manufactured in India to define the possible regions of production. Three glasses were investigated: the m-Na-Al 1, m-Na-Al 2 and m-Na-Al 3 glasses. The strontium and neodymium isotopic composition of the m-Na-Al 1 glass is supporting archaeological evidences suggesting that this glass was produced in Sri Lanka and in south-eastern India. In contrast, although it was assumed that the m-Na-Al 2 glass was produced in Maharashtra, the strontium and neodymium signature of this glass is incompatible with this hypothesis. Isotopic data and historical evidence are pointing instead towards an origin from Uttar Pradesh. The isotopic signatures of the m-Na-Al 2 and 3 glasses are fairly similar. The m-Na-Al 3 glass was discovered in Kopia, eastern Uttar Pradesh, where evidence suggests that glassmaking and glass working took place on-site. The raw material available around the site has an isotopic signature different from the glass showing that ingredients for glass production were brought from elsewhere or that the glass itself was imported to the site to be turned into finished objects. Lead isotope signatures were considered for glass samples containing lead-based or lead-containing colouring ingredients. They indicate two possible provenances for the lead: Thailand and north-western South Asia.