Prismatic obsidian core and blades. AD 600–1500, Culhuacan, Valley of Mexico. Latin American Archaeology, UMMA Expedition. UMMAA 30889.

Obsidian is formed when lava from a volcanic eruption cools rapidly. The resulting volcanic glass has excellent fracturing properties and was highly desired by ancient toolmakers and users. Obsidian sources have distinctive chemical signatures, allowing archaeologists to figure out the source of obsidian artifacts and trace their movement. In 1946, UMMAA archaeologist James B. Griffin collected the prismatic core and fine blades shown here from the site of Culhuacan (AD 600–1500) in the Valley of Mexico. The greenish tint of the material, most visible on the central blade, suggests it comes from Pachuca, about 30 miles northeast of modern Mexico City. Pachuca obsidian was especially renowned for its purity and superb flaking properties and was widely traded throughout ancient Mesoamerica.

Back to Day 27 or continue to Day 29.
