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Obsidian was highly valued by many cultures across Pre-Columbian Mesoamerica, including the Mexica (Aztecs), for its natural lustre and sharpness, which made it a perfect material for both highly polished ornaments and the production of tools. Analysis of obsidian artefacts from the Mexica capital of Tenochtitlan, modern-day Mexico City, reveals a complex story of shifting cultural preferences and expansive trade networks.
The study, recently published in PNAS (https://doi.org/10.1073/pnas.2500095122), examined over 700 obsidian objects recovered during excavations at Templo Mayor – the sacred precinct at the heart of Tenochtitlan – since 1978. The assemblage comprised a variety of objects discovered in both ritual offerings and construction fills across the site’s multiple phases. Portable X-ray fluorescence (pXRF) was used to reveal the objects’ geochemical fingerprints and determine the sources of the raw material.
The results indicate that almost 90% of the obsidian studied came from Sierra de Pachuca, an outcrop c.94km north-east of Tenochtitlan that produces a green- and gold-coloured obsidian known to have been prized by the Mexica for its appearance and for its symbolic connection with the mythical city of Tollan. However, the remaining 10% turned out to reflect a greater variability than expected, with at least seven distinct sources represented, some of them beyond Mexica’s borders and even within territories controlled by rival polities.
The analysis also revealed that almost all of the ceremonial objects in the sample were made from Sierra de Pachuca obsidian, from miniature weapons and jewellery to inlays in sculptures and even decorated human skulls. In contrast, a much greater diversity of sources was present in the blades, flakes, and other tools found in construction fill, which made up a larger part of the collection. This suggests that obsidian intended for everyday use came to the city’s markets from a variety of locations. The study revealed changes in obsidian use over time, as well. In particular, more variety was observed in the city’s early phases, among both ritual and non-ritual objects. After Mexica’s consolidation of power c.AD 1430, obsidian for ritual objects came almost exclusively from Sierra de Pachuca, suggesting an increase in religious standardisation and centralised control.
Already, these findings are improving our understanding of cultural attitudes towards this important resource and the economic networks behind it; further research will doubtless reveal more.
Text: Amy Brunskill / Image: Leonardo López Luján, courtesy of Proyecto Templo Mayor, INAH
