Stone is engineered with fire
Silcrete buried under a fire for hours changes its fracture properties and becomes workable.
- When
- —
- Duration
- 7 thousand years
- Known to
- ± 5 thousand years
- Era
- Late Pleistocene, Quaternary
By around 72,000 years ago, toolmakers in southern Africa were burying silcrete under hearths and heating it slowly to several hundred degrees, which alters its internal structure and makes it far easier to flake into fine blades. The process takes many hours and produces no visible improvement until the stone is worked. It is deliberate material transformation with a delayed payoff — pyrotechnology applied not to food or warmth but to manufacturing.