Designing Experimental Research in Archaeology by Jeffrey R. Ferguson

Author:Jeffrey R. Ferguson [Ferguson, Jeffrey R.]
Language: eng
Format: epub
ISBN: 9781607320234
Barnesnoble:
Publisher: University Press of Colorado
Published: 2010-05-15T00:00:00+00:00

CONCLUDING THOUGHTS

Our results with Wisconsin orthoquartzites essentially confirm Behm and Faulkner’s (1974) more specific study of the thermal alteration of Hixton silicified sandstone. They found that some subtle physical changes occur in Hixton after heating to 245°C for several hours (Behm and Faulkner 1974). Their conclusion was that the most intensely hued colors of Hixton (dark red, brown, black, and honey) occur naturally but that iron oxides within lighter hues of the raw material may darken the stone as a result of thermal alteration (Behm and Faulkner 1974:273–275). Behm and Faulkner provided no criteria to distinguish between natural and thermally altered materials recovered archaeologically.

Behm and Faulkner (1974:275) could not find any evidence that thermal alteration significantly improved the flaking quality of the Hixton samples, in either hard-hammer or pressure flaking efforts. Some of the samples that were thermally altered became very fragile, and some behaved “differently” (Behm and Faulkner 1974:275).

Our study also indicates that heat alteration of orthoquartzite results in few significant changes in the ease or reliability of knapping. It appears that the heating of orthoquartzites at archaeological sites, if truly intentional, was designed to alter the color of the raw material. Also, heating may have been used as a quarrying technique to break up some of the large slabs of raw material, and archaeologically recovered specimens are artifacts of that process, rather than of deliberate heat alteration, in the production of a finished tool (Gregg and Grybush 1976).

Alternatively, further experimentation using higher temperatures may demonstrate that orthoquartzites are possibly enhanced by heat alteration. Rick (1978:18–21) indicates that temperatures of 230–290°C were sufficient to produce color changes but not luster changes in Burlington chert. Temperatures of more than 300°C were necessary for uniform luster changes, but temperatures of 370°C significantly increased the likelihood of raw material burning, decrepitation, and uncontrolled fracturing of material. Replicating our experiments while manipulating controllable variables such as peak temperature and length of heating will provide more complete answers to our questions in the future.

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