Obsidian provenance determination by back-scattered electron imaging

Abstract

Obsidian glass is a significant component of the lithic artefact assemblage of primitive cultures; the ability to characterize and correlate artefacts with specific sources provides significant information about prehistoric patterns of procurement and exchange¹. Because visual and light-optical microscopic methods have proved ineffective in characterizing obsidian, chemical methods such as X-ray fluorescence² (XRF) and instrumental neutron-activation analysis³ (INAA) are usually used to try to determine provenance. Here we show that electron microscopy, specifically back-scattered electron (BSE) imaging, may be used to characterize obsidian petrographically. The variety and number of BSE-observable features are generally sufficient to petrographically 'fingerprint' individual obsidian sources. Sources are also sufficiently homogeneous so that BSE characterization can determine provenance for individual artefacts of archaeological obsidian.