87Sr/ 86 Sr ratios have been determined for glasses from four production sites, dated to between the sixth and the 11th centuries, in the Eastern Mediterranean region. On the basis of elemental analyses, the glasses at each location are believed to have been melted from different raw materials. Two glass groups, from Bet Eli'ezer and Bet She'an, in Israel, are believed to have been based upon mixtures of Levantine coastal sands and natron, and have 87 Sr/ 86 Sr ratios close to 0.7090, plus high elemental strontium, confirming a high concentration of modern marine shell ( 87 Sr/ 86 Sr ~ 0.7092) in the raw materials. The isotopic compositions of these two groups of glasses differ slightly, however, probably reflecting a varying ratio of limestone to shell because the sands that were utilized were from different coastal locations. Natron-based glasses from a workshop at Tel el Ashmunein, Middle Egypt, have 87 Sr/ 86 Sr values of 0.70794-0.70798, and low elemental strontium, consistent with the use of limestone or limestone-rich sand in the batch. High-magnesia glasses based on plant ash, from Banias, Israel, have 87 Sr/ 86 , probably reflecting the isotopic composition of the soils that were parental to the plants that were ashed to make the glass. Strontium and its isotopes offer an approach to identifying both the raw materials and the origins of ancient glasses, and are a potentially powerful tool in their interpretation.

The ability to make rapid measurements on small samples using laser fluorination enhances the potential of oxygen isotopes in the investigation of early inorganic materials and technologies. δ18O and 87Sr/86Sr values are presented for glass from two primary production sites, four secondary production sites and a consumer site in the Near East, dating from Late Antiquity to the medieval period. δ18O is in general slightly less effective than 87Sr/86Sr in discriminating between sources, as the spread of measured values from a single source is somewhat broader relative to the available range. However, while 87Sr/86Sr is derived predominantly from either the lime‐bearing fraction of the glass‐making sand or the plant ash used as a source of alkali, δ18O derives mainly from the silica. Thus the two measurements can provide complementary information. A comparison of δ18O for late Roman – Islamic glasses made on the coast of Syria–Palestine with those of previously analysed glasses from Roman Europe suggests that the European glasses are relatively enriched in 18O. This appears to contradict the view that most Roman glass was made using Levantine sand and possible interpretations are discussed.