Around the world, the prehistoric record is littered with obsidian scrapers, choppers and all-purpose hand axes. Early toolmakers likely chose the volcanic glass because it flakes predictably — it can be shaped more easily than other materials — and the result is a razor-sharp edge.
“The fresh edge of an obsidian flake is just a few dozen atoms thick,” says Ellery Frahm, an archaeological scientist at Yale University. “When viewed under a microscope, a steel surgical scalpel would look like a dull and badly abused ax next to an obsidian flake.”
Obsidian is also brittle, a bonus for hunters.
“An obsidian projectile point creates a lot of damage because it’s sharp and also likely to break inside the animal,” says Albuquerque-based geoarchaeologist M. Steven Shackley, professor emeritus at the University of California, Berkeley. He adds: “If you want to create damage, you want to use obsidian.”
The material’s bold appearance — shiny and usually black, though red and other colors occur — may have made it attractive for symbolic or aesthetic reasons as well. Whatever its appeal, early humans sought it out. Despite its frequent use throughout prehistory, the raw material is not common.
“When that happens, all the elements are frozen inside that glass like a snapshot,” says Shackley. “That’s why we can distinguish all these different sources.”