Aboriginal Thermal Alteration of a Central Pennsylvania Jasper: Analytical and Behavioral Implications

The aboriginal thermal processing of Bald Eagle Jasper in Central Pennsylvania is described in terms of the chemical and physical changes that occur in this material. Heat treatment is shown to transform the jasper's geothite component to hematite and to improve its workability by reducing its fracture toughness by one-half. This is accompanied by a yellow to red color change. The role of thermal alteration in the local lithic technology is inferred from laboratory heating experiments and from an analysis of lithic artifacts from the Houserville Site (36 Ce 65), a jasper workshop. The prehistoric utilization of this material is analyzed from a regional perspective. The results have implications for aboriginal social organization in Central Pennsylvania.