Hammerstones were used to make other stone tools. They required little modification and were chosen for hardness and size. After use, hammerstones develop whitish areas called stone bruising. This happens when the other minerals in the stone are crushed.
Knapping is the process of taking flakes off another stone. Hammerstones were used for a knapping technique known as hard-hammer percussion. For this method, a knapper strikes the core with a hammerstone to break off flakes.
Date: San Dieguito Complex (10,000 ya – 7,500 ya)
Material Class: Lithics – Chipped Stone