Stone Tool Analysis: Impact fracture

Stanly Stemmed Point, USA

Stone weapon armatures—spearpoints, dart points, and arrowheads—often suffer fractures at the tip when they strike hard surfaces.  Archaeologists study the location and nature of impact fractures to differentiate weapon armatures from knives, and to determine the sorts of weapon systems used to launch the projectiles.

Face Shear

High-velocity impact can deliver force at the tip of a point which is exceptionally high relative to the point’s small size.  Sometimes this can initiate flakes which propagate down one or both faces of the point.  The impact fractures are usually initiated by bending or wedging, although conchoidal initiations can also occur.  Due to the disproportionate force relative to point’s mass, the crack path is often unstable, creating closely-spaced or ‘stacked’ undulations on the impact scar.

Hardaway point 3

Hardaway Side-Notched Point

Pedernales impact fracture

Pedernales Point

Stanly Stemmed 1

Stanly Stemmed Point


A burin is a flake struck down the edge separating a flake’s ventral and dorsal surface.  On bifacial tools, a burin is struck down the bifacial edge separating the obverse and reverse faces.  In high-velocity impact, a fracture is often initiated at the point’s tip and the crack propagates down the edge in the same manner as a burin.  

No related artefacts