The petrographic analysis of chert provides a list of characteristics that can be used to identify the stratigraphic origin of artifacts. Hand sample characteristics include vugs, fused sand grains, oolids, and organic structures. Polished and acid-etched slabs may display a full range of textural and color variations present on an intraformational basis. Petrographic thin sections reveal varieties of ooids, dolomite and ankerite euhedra, microstylolitic features, and the presence of sulfides, sponge spicules and radiolaria. We have successfully applied these petrographic characteristics to the identification of chert and other raw material sources throughout the Appalachians, and from Paleoindian through Late Woodland periods.
Other lithic raw materials may have distinguishing characteristics (e.g., phenocrysts in volcanic rocks, grain size and mineral composition in sedimentary and metasedimentary rocks) that can be used to identify probable sources. In many cases, probable matches between artifact materials and raw-material sources (both chert and non-chert) can be made with the aid of our lithic database, although matches can also be made via comparisons with geologic (non-artifact) samples collected from the study area in question.
Thin section analysis is also available for ceramics and ceramic tempers. We have developed special preparation techniques that preserve perishable archeological materials such as fiber, pollen and spores encased within ceramics. Ceramic analysis also includes description of temper types and provenance identification of the minerals present.
***Updated Spring, 2014