Mechanical Properties of Stone Artefact Materials and the Effect of Heat Treatment*

Abstract

Mechanical testing of lithologies used for stone tool manufacture has shown that fracture toughness is the most objective measure of the quality of raw materials shaped by either flaking or pecking/grinding. Materials amenable to pressure flaking and blade manufacture have low values of fracture toughness, whereas those shaped by pecking/grinding have high values. The fracture toughness test is also the most definitive for quantifying the improvement in flaking properties of materials subjected to intentional heat treatment. Cryptocrystalline and macrocrystalline siliceous lithologies demonstrate a well‐defined, gradual reduction in fracture toughness with increased temperature. When heated to optimum temperatures, their fracture toughness approaches that of obsidian, the lithology generally regarded as having the best flaking properties.

Fires at Neumark-Nord 2, Germany: An analysis of fire proxies from a Last Interglacial Middle Palaeolithic basin site

“…Thermal fracture, as observed on many of the studied pieces, has been shown to take place when the material is exposed to temperatures in excess of 400°C (Purdy and Brooks 1971;Domanski et al 1994;Domanski and Webb 1992;Buenger 2003). Although clear-cut correlations between specific characteristics of heating and precise temperatures do not exist , the observed heavily altered flint artifacts (being calcined and strongly fragmented) are very likely to have been exposed to significantly higher temperatures than the minimum temperatures indicated above (i.e., > 300-400°C).…”

Experimental Study on Heat Alteration of Palaeolithic Material: Preliminary Results from Shale in the Northeastern Region of Japan

“…Since the first report on the improvement of flakeability by heating (Crabtree and Butler 1964), several researchers have performed both manual (Flenniken and Garrison 1975;Griffiths et al 1987;Mandeville and Flenniken 1974;Patterson 1979) and mechanical (Domanski et al 1994;Purdy 1974;Purdy and Brooks 1971;Schindler et al 1982) tests on the flaking property of heated rocks. among them, Purdy performed compressive strength tests and point tensile strength tests on Florida chert subjected to various heating conditions.…”

“…Many researchers have reported that fine-grained and coarse-grained materials exhibit different responses to heat (Domanski et al 1994;Mandeville 1973;Sollberger and Hester 1973). It may be assumed that the variability in the results of strength tests in this study was caused by the differences in temperature and durations of heating required for the transformation of each different material.…”

La anisotropía y el clivaje del cuarzo automorfo y sus posibles efectos sobre la talla: Una revisión bibliográfica [Anisotropy and cleavage of automorphic quartz and their potential effects on the knapping: A literature review]

“…Esta característica fue vista como un obstáculo importante para la talla del cuarzo automorfo así como una posible causa detrás de su uso aparentemente anecdótico durante la prehistoria (Collina-Girard 1997;Domanski et al 1994;Mourre 1996). Sin embargo, el registro arqueológico evidencia -por el contrario -que las industrias realizadas sobre cristal de roca tienen una presencia global (Delagnes et al 2006;Desrosiers & Gendron 2004;Sachanbiński et al 2008), jugando incluso un papel importante en muchos contextos del Paleolítico Superior o Mesolítico (Aubry 1998; Bang-Andersen 1998; Pignat 1997) y, desde luego, estando muy presentes en los conjuntos de la Prehistoria Reciente del Occidente Peninsular (Figura 1).…”