Professors of Geology John Millhauser, Enrique Rodríguez-Alegría, and Michael D. Mexico’s igneous geology is also controlled by two tectonic plates, the Carribean plate, and the Cocos plate, which would cause the formation of the volcanoes mentioned above. The central portion of the modern-day country Mexico is home to numerous volcanoes, both active and dormant, from which obsidian was readily available. The Aztecs, no doubt enamored with the sharpness that obsidian could produce, were able to gather large quantities of obsidian, thanks to their unique location. Map of the sites mentioned above for Obsidian Production These specific types of fractures cause obsidian to be incredibly sharp, especially when polished by a trained stone sharpener. Jim Miller, a geologist from Oregon State University, emphasizes that the distinguishing feature of obsidian compared to other rocks is that, like all types of volcanic glass, obsidian breaks on a “conchoidal” or curved fracture. For contrast, granite, which is chemically similar to Obsidian, takes a significant amount of time to cool, thus visible crystals of minerals such as quartz and feldspar form and become dominant within the rock itself. Since the cooling process is rather abrupt, crystal structures within the silica matrix of the lava are cut off from forming, leaving a smooth surface on the outer layer. This lava is then rapidly cooled upon exiting the volcano’s chamber this cooling normally occurs naturally when lava comes in contact with a body of water, such as a large lake or pond.

Obsidian, a type of black volcanic glass, which is the byproduct of volcanic eruptions that eject silica-rich lava onto the surface of the Earth. Within this paper, I hope to shed light on the question of how Aztecs utilized obsidian throughout the various processes of their death culture. This death culture has fascinated historians and scientists alike, with its complexity and rather foreign ideas being the chief driver of this curiosity. The Aztecs used obsidian for a number of special purposes, but perhaps, the most important of these purposes lay within their intricate and often gruesome death culture. One of the most remarkable relationships between humans and local geology that is incredibly well documented, is the Aztecs and their relationship to the igneous rock known as obsidian or a specific type of volcanic glass. Geology and human beings have been linked together in unique and interesting ways since the dawn of human-kind as a species, with many tales of their relationship being recorded, thanks to the invention of writing. Aztec codex image depicting the macuahuitl (Wiki)

Obsidian knife metal detector