Plains Anthropologist Journal Of the Plains Conference

Ethnographic literature of the late 19th and early 20th centuries contains a number of accounts of the use ofheat in the manufacture of chipped stone artifacts.Consistent failure of attempts to duplicate these techniquesled to scepticism regarding any association’ of fire with flint knapping. In 1964, Crabtree and Butler described a technique of thermal pretreatment which improved the working quality of the material and which they believedhad been used aboriginally. Archaeological evidence now indicates that use of this technique was widespread both geographically and temporally.The need for a simple objective test for the identification of thermally pretreated archaeological materials has led to a number of investigations into the nature of chert and of the thermally induced changes which take place. Chert, a microcrystalline silicate, is composed of granular quartz microcrystals in a fibrous matrix. SEM micrographs indicate that fracture in raw chert tends to be intergranular and thatthematrix tears rather than breaking. With the application of heat, the fibrous matrix becomes fused, probablythrough the eutectic development of mineral impurities. The resultant material is more homogeneous and allows more predictable transgranular fracture.