Elemental Compositions and Glass Recipes

Abstract

Glass composition has become a key tool for the study of ancient glass. This approach consists of measuring the concentrations of the different elements present in the glass. Information are then used to identify glass types and glass recipes to infer glass technology, provenance, circulation and sometimes, relative dating. Decades ago, only the major and the minor elements (the most abundant elements) were determined, while nowadays, trace elements (elements present in very small concentrations) are also accessible. With the full glass composition, it is possible not only to distinguish different recipes but also to identify the use of different raw material sources among workshops sharing the same recipes. From 1923 to 1933, the Field Museum and Oxford University excavated the site of Kish, located in modern Iraq, 80 km south of Baghdad. Kish is an ancient city occupied as early as 3200 BCE through the seventh century CE. A little more than 400 glass beads were identified in the anthropology collections at the Field Museum with dating, when available, ranging from the Early Dynastic to the post-Sasanian period. The scarcity of the contextual information for most of the beads as well as an often-poor preservation state created challenges for their study. Using laser ablation—inductively coupled plasma—mass spectrometry, a group of beads from Kish with an uncertain chronology and provenance was analysed. Based on the elemental composition of the glass, a second to first century BCE dating was confirmed and a provenance from South or Southeast Asia was proposed.