Raw materials obtained through long distance exchange networks can be one of the most valuable areas to study in archaeology. They can provide information on social and economic networks as well as giving insights to the meanings, value and identities ascribed to manufactured objects. Obsidian, the naturally occurring volcanic glass, is a particularly useful example. It occurs in very restricted areas of the Middle East, particularly eastern and central Anatolia but from c.9,000 BC was exchanged widely across the Middle East, reaching sites up to 800km from the sources. It is a material that has both functional value, as it can be chipped into very sharp stone tools, and aesthetic appeal, as a translucent and shiny stone that can be shaped into jewellery, vessels and other objects.
Largely because obsidian only occurs at a restricted number of sources, its origin can be determined through chemical analysis. Until recently analyses have been carried out on small samples, often only a handful of artefacts from the possible thousands of artefacts from single sites. More recently new techniques have allowed large scale, non-destructive analyses.
In 2014, the Manchester Obsidian Laboratory was founded as a collaboration between Stuart Campbell (University of Manchester), Elizabeth Healey (University of Manchester) and Osamu Maeda (University of Tsukuba). We use a Niton XL3t 980 GOLDD+ portable XRF analyser (pXRF), ideally suited carrying out analysis of obsidian non-destructively, with very low cost per sample and the ability to take it to museums or into the field. Standardisation is achieved by use of a set of international standards and exchange of samples with other laboratories. To date we have analysed more than 6,500 archaeological artefacts and more than 1,500 geological samples.