hammerstone

noun

1. A type of stone used to hit or strike in a similar way to a modern-day hammer.

   “Striking a hand-held isotropic block or cobble (a core) with a hammerstone initiates a cone-shaped crack at roughly 60° from the axis of force, exemplified by the hole in a plate glass window made by a pellet gun (18, 19 ).”

   “On the other hand, in the same crannog, a hammerstone broken in two was found, each half in a different place, as were two parts of a figurine at Dumbuck.”