The essential mechanics of conchoidal flaking

Flaked stone tools are the most durable and therefore the most common artifacts available to archaeologists for tracing the development of early Man. However, the essential mechanics of conchoidal flake formation has not yet been described. In order to successfully create a relatively thin flake that does not terminate prematurely, the direction of the flaking force has to be reasonably precise. We show that the direction of the flaking force is determined mainly by the stiffness of the flake, the actual angle of the blow or impulse having relatively little effect. Long thin flakes can be easily produced because this direction of the flaking force is very close to that necessary to produce local symmetry at the tip of the crack propagating parallel to the surface of the stone.RésuméLes outils en pierre taillée sont les témoignages les plus durables et, dès lors, les plus courants à disposition des archéologues pour traquer le développement des premiers hommes. On n'a cependant pas encore décrit les mécanismes essentiels de la formation d'une écaille conchoïdale. Pour créer avec succès une écaille relativement mince qui ne soit pas prématurément trop courte, il faut que le direction de la force d'écaillage soit relativement précise. On démontre que la direction de cette force est essentiellement déterminée par la raideur de l'écaille, l'angle réel de percussion ayant, pour sa part, un effet relativement peu important. Il est possible de réaliser des écailles longues et minces dès lors que la direction de la force d'écaillage est très voisine de celle nécessaire à produire une symétrie locale à l'extrémité d'une fissure se propageant parallèlement à la surface de la pierre.

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