Itztli: The Story of Obsidian

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Few materials have shaped the daily and spiritual life of Mexico as profoundly as obsidian, known to Nahuatl-speaking peoples as itztli. This volcanic glass, born in the fiery hearts of the country’s great mountain chains, was simultaneously tool, weapon, currency, mirror, deity, and blood-letter. For more than ten thousand years, from the first hunter-gatherers who flaked spear points on the shores of ancient lakes to the Aztec priests who sliced open royal chests on temple pyramids, obsidian remained indispensable. Its edge is sharper than surgical steel, its shine captures souls, and its blackness drinks light. Mexico without obsidian is almost unimaginable.

The story begins in geology. Obsidian forms when silica-rich lava cools so quickly that crystals have no time to grow. In Mexico this happened repeatedly along the volcanic axis that runs from the Pacific coast to the Gulf of Mexico: the Trans-Mexican Volcanic Belt, the western Sierra Madre, and scattered peaks in Chiapas and Veracruz. The most famous sources were destined to become the great quarries of Mesoamerican civilization. Pachuca produced green obsidian, Ucareo-Zinapécuaro had grey and black, Pico de Orizaba’s had a golden sheen, and the Otumba mines were known for its opaque grey stone. Each source produced glass with a slightly different chemistry, color, and fracture pattern, allowing archaeologists today to trace a blade from a Maya king’s tomb straight back to the mountain that birthed it.

The earliest evidence of human use of obsidian comes from the Pleistocene. At Tlapacoya, southeast of Mexico City, obsidian flakes have been found in layers dated to 21,000 to 23,000 years ago, making them among the oldest worked tools in the Americas. By 9000 BC, during the Archaic period, small bands of foragers were systematically visiting outcrops in the Valley of Mexico and the Basin of Puebla-Tlaxcala to knap prismatic blades and dart points for atlatls. These early hunter-gatherers already understood that obsidian from certain flows was superior; they walked hundreds of miles to reach the green deposits of Pachuca rather than use the mediocre local glass.

With the arrival of agriculture and settled villages around 2000 BC, demand exploded. Obsidian became the steel of the Preclassic era. A single skilled stone knapper working with a copper-tipped pressure tool could produce hundreds of razor-sharp prismatic blades from one polyhedral core. These blades were used for everything: harvesting maguey fibers, cutting deer hide, shaving hair, and, increasingly, drawing human blood for the gods. By the time Teotihuacan rose in the first century BC, obsidian workshops covered entire neighborhoods. Excavations at the city’s Oztoyahualco compound revealed floors littered with millions of flakes and cores; one workshop alone is estimated to have produced 400,000 blades per year.

Trade networks grew accordingly. Green Pachuca obsidian, unmistakable because of its golden inclusions, has been found as far north as the high plains of Coahuila and as far south as the Maya lowlands of Copán and Tikal. Grey Otumba obsidian dominated central Mexico, while the black glass of Ucareo and Zaragoza reached the Gulf Coast and the Huasteca. In the Classic period, Maya cities imported obsidian from highland sources in exchange for cacao, quetzal feathers, and marine shells. Chemical sourcing studies show that a single eccentric flint from the Cenote of Sacrifice at Chichén Itzá contains obsidian blades from at least five different Mexican highlands sources thus proving of the sophistication of these exchange systems.

Control of the obsidian mines was often political. The ancient Mexican powerhouse of Teotihuacan appears to have monopolized the Pachuca source through a combination of alliances and military pressure. When the city collapsed around 650 AD, the green obsidian trade fragmented, and new powers—the Toltecs at Tula, later the Tepanecs and Acolhua—fought bitterly for access. By the fifteenth century the Aztecs had turned obsidian into an instrument of empire. They conquered the mining towns around Pachuca and stationed garrisons there. Ancient Aztec tribute records and the Codex Mendoza list thousands of bundles of obsidian blades and cores delivered annually from subject provinces.

Mining itself was surprisingly large-scale. Spanish chroniclers described open pits and galleries at Pachuca that went dozens of meters deep. Workers lit fires against the rock faces to crack them and then pried off blocks with wooden levers. At the surface, professional stone knappers reduced the rough nodules into manageable cores. The best cores were carried intact to cities; lower-grade material was worked on site into rough blanks. Archaeological surveys have located hundreds of quarry workshops around the Sierra de las Navajas, some covering several hectares and littered with billions of flakes.

Practical uses for obsidian were endless. Farmers used blades set into wooden sickles to harvest maize. Artisans cut shell, wood, and feathers with them. Barbers shaved nobles’ heads into distinctive hairstyles. Warriors carried macuahuitl which were oak clubs edged with obsidian blades that could decapitate a horse, as the startled conquistadors learned in 1520. Surgeons performed skull drilling and amputations with obsidian scalpels. The edges of these scalpels were so sharp that wounds often healed with minimal scarring.

But obsidian’s most dramatic role was ritual. It was the preferred material for bloodletting and sacrifice because it symbolized both life and death: Its sharpness drew blood, and its blackness evoked the underworld. Priests pierced tongues, earlobes, and other body parts with stingray spines or obsidian lancets, letting blood drip onto paper strips that were then burned to feed the sun. On major festivals, captives were stretched over techcatl stones while a priest wielding a wide obsidian knife opened their chests in a single stroke. The hearts, still beating, were raised toward the sun before being placed in cuauhxicalli eagle vessels, often carved from stone but sometimes from obsidian itself.

Obsidian mirrors were the exclusive property of priests and rulers. Polished to a high gloss on one side, they were believed to allow communication with the spirit world. Tezcatlipoca, “The Smoking Mirror” who was the supreme sorcerer god, carried one as his emblem. Several stunning examples survive, including the black mirror found in the tomb of Pakal at Palenque and the British Museum’s mirror that once belonged to John Dee, Elizabeth I’s court astrologer.  For more about John Dee’s magical Mexican mirror, please see Mexico Unexplained episode number 161. Large, elaborately chipped representations of scorpions, serpents, or human figures were buried as offerings in caches beneath temple stairs and ballcourts. The largest known cache, from the Pyramid of the Moon complex at Teotihuacan, contained obsidian carvings weighing several pounds each. In the Postclassic period, the Mixtecs of Oaxaca took obsidian artistry to its peak, producing delicate knives with mosaic handles of turquoise, shell, and gold for royal funerals.

The arrival of the Spanish abruptly ended obsidian’s dominance. Steel was tougher, could be reforged, and did not shatter on impact. Within a generation, indigenous stone knappers found themselves reduced to making cheap blades for peasant tools or trinkets for the colonial market. Yet obsidian never completely disappeared. Rural communities continued using blades for maguey scraping and tortilla cutting well into the twentieth century. Today, artisans in San Juan Teotihuacán and Magdalena Chichicaspa still produce knives, arrowheads, and jewelry for tourists, working the same green and grey glass their ancestors mined. Anyone who has been to any of the major archaeological sites in Mexico has most likely been approached by a vendor selling an obsidian statue of an ancient god or a special blade which he claims dates back to the Toltecs.

Modern science has revealed just how extraordinary the material remains. Obsidian hydrates at a predictable rate when freshly broken, allowing precise dating of archaeological sites. Its chemical fingerprinting has revolutionized our understanding of ancient trade. Surgeons experimenting with obsidian scalpels in the 1970s found that incisions made with obsidian heal faster and with less scarring than those made with steel, confirming what Mesoamerican healers knew all along. From the spear points of Ice Age hunters to the sacrificial knives of Huitzilopochtli’s priests, obsidian was more than a raw material, it was a bridge between earth and sky, between the practical and the sacred. In its flawless black surface, generations of Mexicans saw both the reflection of their own faces and the dark gaze of the gods. Even now, when the wind moves across the abandoned ancient quarries, the broken edges still glint like a thousand tiny mirrors, remembering everything.

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