OBSERVATIONS ON BROKEN POINTS: EXPERIMENTAL DATA

SOCIETY FOR CALIFORNIA ARCHAEOLOGY
Mach 29, 1984, Salinas, California.
Program Abstract: Coyote Press.

Harwood, Ray and Cay Singer
Northridge Archaeological Research Center

OBSERVATIONS ON BROKEN POINTS: EXPERIMENTAL DATA

A series of experiments were conducted to determine something about the variables affecting the breakage patterns of projectile points. Thirty identical points were made from fused shale (a local meta-sedimentary Sio2), and then hafted to three different types of arrow-shafts: 1) One-piece solid hardwood, b) two piece hardwood, and c) two-piece hardwood and cane. The three groups of arrows, ten of each type, were shot at identical
Wood plank targets with hand held bow from a distance of 25 feet (8m). More than 90%
Of the points broke on impact leaving the broken tip imbedded in the plank. Breaks occurred either at the tip or midsection, sometimes accompanied by basal fractures (broken tangs0. Both hinge and languette fractures were generated but no burinations occurred in the thirty trials conducted. Fracture type and location appear to be strongly correlated with hafting form and style of shaft. Compound shafts of wood and cane seem to absorb more shock on impact and therefore fewer points are broken. Also, breaks tend to occur closer to the tip with compound shafts. Points with broken tips are easily resharpened and reused, whereas medial breaks usually render the point useless as a projectile. Broken projectile points from archaeological contexts may be understood more clearly if the cause and mechanisms of use-fracture are better understood.