| Taphonomy of artefacts
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| Although controlled heating of rocks can improve their flaking qualities, uncontrolled heating of rocks can degrade their flaking properties and even cause them to shatter. This can happen easily when camp fires are placed near to rock fragments (including stone artefacts). Two examples of the consequences of heat shattering are illustrated here.
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| The photograph to the right shows a scar created by the explosion of a 'potlid'. Potlids are plano-convex fragments of stone ejected from a larger block of stone (or artefact) as a result of rapid expansion of the rock during uncontrolled heating. These potlids, or the scars they leave behind, never have ringcracks or any other feature indicative of the application of a blow. The potlid scar is often deepest in the centre, indicating an internal initiation of the fracture. |  |
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| Another feature created by uncontrolled heating is a grid of cracks in the rock surface. This pattern of cracks, called 'crazing', occurs during rapid heating or cooling. |  |
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| These results of uncontrolled heating have a negative effect on the usefulness of the rock for flaking. By creating scars and cracks in the rock these processes effectively make the rock much less homogeneous than it had been, and can make it impossible to control fracture. In addition the scars have sometimes been mistaken for the scars created in stoneworking. These processes of uncontrolled heating, together with other degradational processes, are known as taphonomic processes as they modify the archaeological material. Further information of the importance of these taphonomic processes is available here.
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For additional information see:
Purdy, B.A. 1975 Fractures for the archaeologist. Pp.133-141 in E.Swanson (Editor) Lithic Technology. Making and using stone tools Mouton Publishers.
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Author: Peter Hiscock, Dept. Archaeology and Anthropology, Australian National University.
Feedback:  peter.hiscock@anu.edu.au.
Date Last Modified: Thursday, 1-May-97
URL: http://artalpha.anu.edu.au/web/arc/resources/intro/tapho.htm
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