Top image: The edge of one of 500 obsidian mine shafts found in Central Mexico recently, which is shedding new light on pre-Hispanic Teotihuacan commerce and trade.

Obsidian mines mined by the pre-Hispanic Mesoamerican tribes of Central Mexico, located just 31 miles (49.88 kilometers) northeast of the ancient city of Teotihuacan, were discovered by archaeologists in earlier this week. More than 500 obsidian mine shafts in the Sierra de la Navajas have been uncovered, helping researchers gain new insights into the daily obsidian mining operations during the Teotihuacan era, which was at its peak from about 1500 AD.

This highly useful material was transported from the obsidian mines and then refined and worked on in workshops. Archaeologists and historians working at the site have no idea yet of how extensive this “cottage” industry was. Additionally, ceramic pieces and architecture containing obsidian pieces from the Teotihuacan period have also been discovered and are under examination, according to the INAH press statement .

Inside one of the more than 500 pre-Hispanic obsidian mine shafts recently discovered in the Sierra de las Navajas mountainous area of Central Mexico, 31 miles (49.88 kilometers) northeast of the ancient city of Teotihuacan.

Obsidian Mines and Obsidian Value in Pre-Hispanic Societies

“The main production in the deposits of the Sierra were the preforms, and considering that Teōtīhuacān carving is very special, to the extent that a single wrong blow can ruin the raw material, it should have been more efficient to make the preforms in the deposit and finish the spikes in Teōtīhuacān,” said Alejandro Pastrana Cruz from the Directorate of Archaeological Studies of the National Institute of Anthropology and History.

Obsidian is known to be one of Mesoamerica’s most important materials, with Teotihuacan controlling the trade of this valuable commodity, roughly between the 1st century AD and 600 AD. It is safe to say that for thousands of years, people living in the Sierra de las Navajas area have exploited the rare deposits of this semi-precious stone.

Obsidian is a type of black volcanic glass, formed when lava cools after coming out of a volcano. It is rich in the lighter elements like silicon, oxygen, aluminum, sodium, and potassium, as it comes from felsic lava. Felsic lava cools down at a fast rate and forms into a crystalline volcanic glass that turns into a variety of colors: ranging from black and grey to green and blue, depending on the location where it was formed.

Over time, it became a highly integrated material in daily and ritual life, so much so that its use is often touted as a reason why the Mesoamericans lacked advanced metallurgy skills. Its hard and sharp edges helped with cutting, tools, rituals (and instruments of worship), and military weapons that were centralized and mass produced in Teotihuacan, according to a Historical Mx report.

This deadly and durable obsidian stone arrowhead is representative of the weapons from the Mesoamerican region long before the Spanish arrived.

Teotihuacan would send skilled stone workers to the obsidian mines and mine the green (the Sierra de la Navajas region is famous for its green obsidian) and blue obsidian from under the volcanic ash .

After this, the black and grey obsidian was selected to use in the manufacture of sharp-edged projectile points and knives. Artifacts would be shaped with techniques used by skilled stone workers who developed the art of lapidary (cutting, polishing, or engraving gems) in Mesoamerica.

Exploiting the Obsidian Mines of Teotihuacan

These particular mines were likely exploited by the Triple Alliance and the Toltecs between 950 and 1251 AD, according to the research titled the “Teotihuacan Project, 60 Years 1962-2022.” Alejandro Pastrana Cruz, an INAH researcher working on this project, explains that Teotihuacan was a complex society having military, commercial, religious classes, and institutions that heavily relied on obsidian.

Between 150 BC and 650 AD, he noted, obsidian was used in artisanal processes, producing weapons, and instruments of worship. It was also represented in art and religious murals .

Heap of surplus obsidian that came from a rich source of obsidian mine shafts in the Sierra de las Navajas mountains of Central Mexico.

Heritage Daily reports that among the discovered mines, the researchers faced a major challenge. This was in identification of dates from the Teotihuacan period – many mines had been reused or sealed during the Toltec exploitation of the region. The Toltecs were a pre-Columbian Mesoamerican culture, who reached their prominence between 950 and 1150 AD.

In fact, they were seen by the Aztecs as their intellectual and cultural predecessors. These same mines were later exploited by a Triple Alliance of the Aztecs represented by the three Nahua city-states of Mexico - Tenochtitlan, Tetzcoco, and Tlacopan - during the 16th century AD. This alliance and the administrative functioning of the Toltecs has given rise to the idea over time that the obsidian industry was highly centralized.

To this extent, and this precarious history, archaeologist Alejandro Pastrana Cruz calls for the preservation of the natural environment of the Sierra, and for collective awareness of the looting of this vitreous rock. He has described obsidian as “geologically and chemically unique in the world.”

Some questions about how so many ancient empires have exploited and utilized this rock remain unanswered, and future research is likely to shed light on it.