The Aztecs used obsidian, a naturally occurring volcanic glass, to make the cutting blades set into macuahuitl swords. The weapon had a wooden body with sharp obsidian pieces embedded along its edges, producing a devastating slashing surface.
Obsidian was valuable because it could be fractured into extremely thin, sharp edges through controlled knapping. Several obsidian sources lay near the Valley of Mexico, including the deposits of Sierra de las Navajas, whose name means “Razor Mountains.” The material was used for many other tools as well, including knives, scrapers, drills, arrow points, and ceremonial objects.
Macuahuitl were not steel swords, and calling them swords can obscure how they worked. They were closer to wooden weapons lined with replaceable cutting elements. Obsidian could be sharper than steel but was also brittle, so its edges could chip or shatter when striking hard materials such as bone, armor, or another weapon. Jade, copper, and flint were not the standard blade material described for the Aztec macuahuitl.