The Isle of Portland, Portland chert and Neolithic arrowheads: qualities and connections

Portland chert occurs in a restricted geological setting and is known to have been selected for manufacturing stone tools in prehistory, particularly arrowheads. This paper investigates the physical properties of this type of chert that made it an excellent material for making arrowheads. Replication experiments were undertaken, which revealed the qualities of Portland chert that made it suitable for arrowhead fabrication are enhanced by heat-treatment. These experiments also explored the reason for the associated distinctive chert debitage that has been observed in archaeological assemblages. This research highlights that arrowheads fabricated with heat- treated chert display a characteristic lustrous appearance also observed in archaeological material. In addition, it considers the selection of this material for use in stone tool production. As Portland chert occurs alongside flint, its use implies choice. Considerable effort would have been expended in the collection, transportation, and exchange of materials with particular physical and aesthetic qualities in prehistory. In addition, other factors may have been important, such as raw material location and place within the landscape. The results of this study suggest that Portland chert was selected for both pragmatic reasons and perhaps because the main source of this material was from a remarkable location. Full reference: Stewart R.J. 2017. The Isle of Portland, Portland chert and Neolithic arrowheads: qualities and connections. Lithics: the Journal of the Lithic Studies Society 38: 57–71. Keywords: Portland chert, Neolithic arrowheads, heat treatment, experimental knapping, Isle of Portland