Jalisco’s obsidian deposits are thought to be the fourth largest in the world. And because pre-Hispanic civilizations in Mexico did not know how to work metal, obsidian was literally a “gift of the gods” allowing them to manufacture arrow and spear heads, knives, scrapers and even mirrors.
These are just two of the many nuggets of information that I gleaned from Mexico’s first Symposium on Obsidian Research and Characteristics, held at the Colegio de Jalisco in Zapopan from October 1–3, with around 60 people in attendance.
The event was organized by archaeologist Rodrigo Esparza, who specializes in the identification of obsidian by Neutron Activation Analysis, a technology that creates a unique “fingerprint” indicating that an artifact could only have come from a certain deposit. The technique has already proven that the Anasazi Indians were using tools which could only have come from obsidian deposits in Jalisco, he said.
Esparza also revealed the findings of a new study of great interest to specialists attending the symposium that deals with pre-Hispanic techniques that produced a kind of obsidian jewelry found exclusively in the region of what today is called Jalisco.
Around 180 B.C., artisans living and working around today’s pueblos of San Juan de los Arcos and Navajas mastered a technique for producing sheets of obsidian a mere one or two millimeters in thickness, Esparza said. “This was not done by grinding or polishing but by using complicated percussion techniques.”
Esparza believes a new-world version of what is called the Kombewa Method of working obsidian was mastered over 2,000 years ago by artisans of the Teuchitlan Tradition. With this technique, they produced obsidian flakes that were slightly convex on both sides, tapering to a very thin edge.
Samples of their creations are prominently displayed in the museums of Tala and Ameca. A necklace of paper-thin obsidian coyotes and another of human figures can be seen in the Tala museum. In Ameca you can see a pectoral necklace made up of around 100 thin disks. In all the cases, these pendants have been pierced for stringing.
“If producing the thin disks was complicated, putting a hole in them was even trickier,” said Esparza.
Using a scanning electron microscope, the researchers discovered nearly invisible marks around the holes in the obsidian disks, suggesting that the ancient artisans used an abrasive material such as ground flint or quartz to help a very fine auger of horn or bone drill a hole through the volcanic glass.
Obsidian formation
The symposium also featured a presentation by geologist Chris Lloyd on the mechanisms of obsidian formation, using a large flow west of Ahuisculco as an example.
He pointed out that a shiny lump of black obsidian, a feathery light piece of pumice and a naturally formed ball of rhyolite (like one of the famed Piedras Bola of Ahualulco) are all basically composed of the same minerals. The difference, he said, is in the water and air content. (For example, obsidian has around one percent water content, but rhyolite has around five percent; and a piece of pumice has so much air that it floats.)
Lloyd also demonstrated that the Piedras Bola are megaspherulites formed by conditions similar to those which produced the thousands of spherulites at the entrance to Ahuisculco’s Selva Negra Nature Reserve.
The obsidian symposium included a field trip to the Selva Negra Nature Reserve at Ahuisculco, where many obsidian mines and workshops have recently been discovered, some of them surrounded by thousands of broken or imperfect knives, scrapers and other tools used in Mexico before the advent of metal-working.
The event ended with a meal prepared by chef Maru Toledo, Jalisco’s most famous expert in traditional cuisine.
Esparza qualified the inaugural symposium a success, noting, that attendees seemed “happy about everything.”
Perhaps of most importance, he stressed, was the forging of an agreement to standardize procedures and establish protocols for taking and analyzing obsidian samples.
“We were also able to establish a data bank of ‘fingerprints’ for raw obsidian from deposits throughout Mexico and we plan to create a litoteca or mineral collection which will contain samples from all over the country.”