Stone Tool Analysis: Overstruck termination
As the crack grows and starts to lose energy, the force angle can become too small, resulting in an imbalance between compression and shearing forces. The stiffness of the flake causes the crack to curve towards the interior of the core, lopping off the core’s base. This is referred to as an overstruck, overshot, outrepassé, or reverse-hinge termination.
Overstruck terminations are generally considered a stoneworking mistake. This is particularly true in blade-making because it can dramatically shorten the core. Overstriking is overcome by using strong core support to ensure that the compression force maintains the crack straight to the bottom of the core. Careful use of the indirect percussion technique—which can increase the shearing force relative to the compression force—can achieve a similar effect without using core support. In sophisticated biface manufacture, just barely lopping off the opposite edge of the biface (in effect, the core base) is considered a demonstration of a flintknapper’s skill.