Experimental Identification of Heat-Treated Silcrete Using Colorimetry and Reflectance Spectrophotometry

Summary

This is an abstract from the "Human Origins Migration and Evolution Research Consortium Poster Symposium" session, at the 86th annual meeting of the Society for American Archaeology.

The heat treatment of stone for tool production represents one of the oldest technologies for transforming the material properties of a natural product to better suit human needs. The earliest evidence for such technology is the heat treatment of silcrete at the South African Middle Stone Age site Pinnacle Point 13B, ~164,000 years ago. Despite its importance for early human technology, relatively little is known about the origins of heat treatment due to methodological constraints faced by researchers. Traditionally, archaeologists identified heat treatment using color change determined by an expert analyst. This is a relatively reliable method, but it is difficult to replicate across analysts and studies. To address this issue, we used a UV-Vis-NIR spectrophotometer to record nanometer-scale wavelength reflectance and calculate CIE L*a*b* color values for experimentally heat treated and unheated silcrete from three South African sources, with multiple nodules from each source. Results indicate quantitative colorimetry can discriminate between unheated and heat-treated silcrete with an average accuracy of 90%. Further, our results show that colorimetry can identify heat treatment in silcrete without knowing geochemical provenience, which is important for analyzing archaeological assemblages. Our study suggests that colorimetry is a promising new approach to studying heat treatment.

This Resource is Part of the Following Collections

• Society for American Archaeology 86th Annual Meeting, Online (2021)   •
• Human Origins Migration and Evolution Research Consortium Poster Symposium

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Record Identifiers

Abstract Id(s): 33014