Pompeii’s Black Mirrors: Art-Historical and Scientific Investigations of Obsidian and Related Materials in the Roman World

A small set of four slabs made of a dark, glass-like material has been recovered from the houses of Roman Pompeii. These panels were included in painted walls as ‘mirrors’, a functional use without parallels in the archaeological record form the Roman world. Scholars have generally identified the panels to be composed of obsidian. This article explores the function and meaning of these artefacts in the context of the Roman discourse on matters and their qualities, both physical and ethical. The owners and decorators of the houses of Pompeii chose these pieces for both their exotic flavor and, more importantly, their potential to be compared to or contrasted with a variety of other materials and techniques (such as water, marble, silver, and wall plaster). This argument relies on the results of two on-site studies, which included characterization of the panels by means of both micro-Raman spectroscopy and portable X-ray fluorescence (XRF). Provenance analysis indicates that the panels were likely created using an artificial material, with the aim of imitating the physical and optic effects of obsidian.