The provenance of ancient man-made glass: Raw materials and the use of chemical and isotopic analytical techniques

The differentiation of glass-making traditions between primary production centers in the ancient Middle East based upon chemical differences is a difficult process because the complexities of glass manufacture can change the composition of distinctive original raw materials. However, when used in conjunction with the measurement of radiogenic isotopes, chemical analyses can provide an improved assignment of geological provenance for plant ash glasses based upon differences in strontium (Sr) and neodymium (Nd) isotopic ratios. The ⁸⁷Sr/⁸⁶Sr ratio found within semidesert halophytic plants reflects the relative geological age of the lime present in the soil in which the plants grow, and the ¹⁴³Nd/¹⁴⁴Nd ratio in silica also reflects its relative geological age. Each of these ratios is maintained throughout glass production and provides a measure of provenance. The ability of isotopic analysis to characterize glass from a primary production center, and to distinguish it from imported items, is illustrated with a case study on the primary glass-making site of Al-Raqqa, Syria.