The Aztec — or Mexica — people oversaw an extensive economic network that involved trade with communities outside of the Mexica Empire, even rivals. By examining more than 700 artifacts from the Templo Mayor of Tenochtitlan in the largest study of its kind to date, archaeologists writing in Proceedings of the National Academy of Sciences highlight the extent of this trade and the influence it had on life and politics in Tenochtitlan, the Mexica Empire’s capital.“This kind of compositional analysis allows us to trace how imperial expansion, political alliances, and trade networks evolved over time,” lead author Diego Matadamas-Gomora, a Ph.D. candidate in Tulane’s Department of Anthropology, said in a press release.Trade Networks from Ucareo to TulancingoArchaeologists from Tulane University analyzed a total of 788 obsidian objects from the Templo Mayor of Tenochtitlan using portable X-ray fluorescence (pXRF). This technique enabled the team to identify the geochemical fingerprints for each item and determine where exactly the artefacts originated from.Obsidian – volcanic glass formed by rapidly cooling lava – was a treasured commodity, used in the production of prized ornaments, such as mirrors, jewellery, and miniature weapons, as well as more practical objects, like cutting tools. Interestingly, while the horde revealed a clear preference for green obsidian from the Sierra de Pachuca mountain range, situated 94 kilometers northeast of Tenochtitlan, there were artifacts containing obsidian from seven other locations – possibly more.This included areas such as Ucareo, which is situated to the west of what is now Mexico City and would have existed beyond the Mexica’s political borders. Otumba, Tulancingo, and El Paraíso were additional sources of obsidian. This suggests that the Mexica’s economy benefited from long-distance trade, including trade with communities that lay outside their region of control and may have been considered rivals. “Although the Mexicas preferred green obsidian, the high diversity of obsidian types, mainly in the form of non-ritual artifacts, suggests that obsidian tools from multiple sources reached the capital of the Empire through [the] market instead of direct acquisition in the outcrop,” Matadamas-Gomora explained in a press release. While obsidian from multiple locations was present, volcanic glass collected from Sierra de Pachuca was prized above all others. Almost 90 percent of the objects sampled contained obsidian from this region, including nearly all ceremonial artefacts. The significance of this rock stems from its green hue and its association with the mythical city of Tollan. In contrast, obsidian originating from elsewhere was more likely to appear in less precious objects, such as blades. The researchers say this suggests less prestigious obsidian would have been traded at local markets and bought by members of the public.How Trade Changed Over TimeThe analysis enabled archaeologists to envisage how obsidian use changed as the empire grew and consolidated. Specifically, there was a sharp dip in the variety of obsidian types used in ceremonial objects from 1430 C.E., which the researchers attribute to increasing levels of centralized control and religious standardization. Prior to 1430 C.E., objects designed for ritual and everyday purposes contained a greater proportion of obsidian located outside the Sierra de Pachuca region. From 1430 C.E. onwards, objects intended for ceremonial use were almost entirely made from Sierra de Pachuca obsidian.Tracking the origin of obsidian throughout the empire also shows how the Mexica’s political influence and access to resources changed over time. Whereas obsidian originating from Tulancingo, El Paraiso, and Zacualtipán was more prevalent earlier in the empire’s history, obsidian from Otumba, Paredón, and Ucareo became more common after 1430 C.E.Combined, these findings offer novel insights into the scale of trade networks in pre-Columbian America and how power and commerce shifted over time.Article SourcesOur writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:Proceedings of the National Academy of Sciences. Compositional analysis of obsidian artifacts from the Templo Mayor of Tenochtitlan, capital of the Mexica (Aztec) EmpireRosie McCall is a freelance writer living in London. She has covered science and health topics for publications, including IFLScience, Newsweek, and Health.