Templo Mayor Yields More Secrets - Spring 2025
Mexico City.- Imagine pulling a forgotten diary from a dusty attic, and suddenly, entire chapters of your family's history come to life. That's precisely what archaeologists are doing at Mexico City's sacred Templo Mayor, but instead of old journals, they're "reading" tiny chips of volcanic glass, and the story they're telling is utterly fascinating.
A new, groundbreaking study, concluded in May 2025, has just revealed that the mighty Mexica empire – the civilization at the heart of what we now call Mexico – was far more sophisticated in its trade than we ever fully understood. Forget simple supply chains; their world was a bustling, complex marketplace, even exchanging goods with rivals, defying previous assumptions about their centralized power.
Leading this incredible detective work is archaeologist Diego Matadamas Gomora. His team, a collaboration between Mexico's National Institute of Anthropology and History (INAH) and Tulane University in the U.S., analyzed a staggering 788 obsidian artifacts found within the sacred Templo Mayor. These pieces, dating back to the Mexica's heyday between 1375 and 1520, tell a rich tale of commerce.
While the famous green obsidian from the Sierra de Pachuca quarry was indeed their top pick, the study's high-tech X-ray analysis pinpointed origins from at least seven other Mesoamerican locations. Think of it: a piece of sacred mirror or a sharp knife used in a Tenochtitlan ritual could have traveled hundreds of miles, crossing territories that weren't always friendly.
"Obsidian diversity increased as Tenochtitlan's power solidified," explains Matadamas Gomora. "In the early phases, it was mostly just Pachuca and Otumba obsidian. But after they defeated Azcapotzalco and formed the Triple Alliance, there was an abrupt shift – going from two or three sources to up to seven." This suggests a thriving market system that grew along with the empire.
This discovery is a major win for archaeologists, as it refines long-held theories. Many experts debated whether the Mexica state strictly controlled all trade, or if goods moved more freely. "Based on our information, both systems coexisted," Matadamas Gomora confirms. Goods, like valuable obsidian, flowed even from enemy or independent regions such as Tlaxcala and the Purépecha lands. "These goods... appear to have been above state restrictions," he added, painting a picture of a surprisingly dynamic and interconnected economy.
The highly-prized green obsidian from Pachuca, known as toltecaliztli, held particular significance. Its unique color and quality made it a favorite for priests and elites, who crafted intricate ritual objects from it. Now, thanks to meticulous work from the Templo Mayor Project team and advanced analysis, we can trace these sacred materials back to their geological birthplaces.
This remarkable study isn't just about rocks; it's about understanding the intricate lives, beliefs, and economic savvy of one of history's most fascinating empires. The humble obsidian chip, once a tool or an offering, has become a silent messenger, revealing the complex, vibrant heartbeat of ancient Tenochtitlan.
Technology Used
Recent research on obsidian artifacts found at the Templo Mayor in Mexico City has heavily relied on a high-tech X-ray technique called portable X-ray fluorescence (pXRF) spectrometry.1 This method is considered "high-tech" due to its ability to provide detailed elemental analysis of materials in a non-destructive and often on-site manner.2
Here's a breakdown of how it works and its significance in the Templo Mayor obsidian studies:
How Portable X-ray Fluorescence (pXRF) Works:
X-ray Emission: The pXRF device emits a beam of X-rays onto the surface of the obsidian artifact.3
Elemental Excitation: When these X-rays interact with the atoms in the obsidian, they cause the inner-shell electrons of those atoms to become "excited" and jump to a higher energy level.
Fluorescence and X-ray Emission: To return to their stable state, these excited electrons fall back into their original shells, emitting secondary X-rays in the process.4 These emitted X-rays are called "fluorescent X-rays."
Unique Elemental Fingerprint: Crucially, the energy and wavelength of these fluorescent X-rays are unique to each element present in the material.5
Detection and Analysis: The pXRF device's detector captures these fluorescent X-rays, and its software analyzes their energies and intensities. This allows researchers to identify the specific elements present in the obsidian and their relative concentrations.
Why pXRF is High-Tech and Ideal for Templo Mayor Obsidian:
Non-Destructive: This is a paramount advantage for archaeological artifacts. The pXRF analysis does not damage the obsidian in any way, preserving these invaluable historical objects.6
Portability and On-Site Analysis: The "portable" aspect means researchers can bring the equipment directly to the Templo Mayor site or the museum where the artifacts are stored.7 This eliminates the need to transport fragile and sometimes numerous artifacts to a specialized lab, saving time, effort, and reducing risk of damage.8
Geochemical Fingerprinting: Different geological sources of obsidian have unique trace element compositions due to the specific volcanic processes that formed them. By analyzing the elemental "fingerprint" of an obsidian artifact, researchers can compare it to known geological obsidian sources.9
Tracing Trade Networks: This ability to "source" the obsidian (determine its origin) is incredibly powerful for understanding ancient trade networks.10 The recent studies at Templo Mayor used pXRF to identify that while the Mexica (Aztecs) heavily preferred green obsidian from Sierra de Pachuca for ritual objects, they also obtained obsidian from at least seven other sources, including those from rival territories like Ucareo.11 This reveals the complexity of their economic and political interactions.
Uncovering Cultural and Economic Practices: By analyzing a large sample of artifacts (the recent study analyzed 788 pieces), researchers can track changes in obsidian sourcing over time and correlate them with sociopolitical transformations within the Mexica Empire.12 For example, the studies show a shift towards almost exclusive use of Pachuca green obsidian for ritual items after the empire consolidated power around 1430 CE, suggesting increased centralization and religious standardization.13
In essence, the high-tech pXRF X-ray allows archaeologists to "read" the chemical composition of ancient obsidian, providing an unprecedented level of detail about the origin, movement, and cultural significance of this vital material in the Aztec world.14
