INVESTIGATION OF THE TRACE CHEMICAL CONSTITUENTS IN CHERT BY REFLECTANCE INFRARED MICROSPECTROSCOPY

X-ray diffraction, reflectance infrared, and transmission infrared data for four visually distinct chert types are presented. These four types include Dover chert (west-central Tennessee), black Ft. Payne chert (west-central Tennessee), red Horse Creek chert (northwest Alabama, northeast Mississippi, and south-central Tennessee), and Burlington chert (east-central Missouri). We also present our laboratory technique (including placement and orientation of the sample) for obtaining high quality spectra of chert using reflectance infrared microspectroscopy. X-ray diffraction (XRD) data were collected on powdered chert samples, as well as on small chips. DIFFRAC^plus EVA Bruker AXS software was used to identify trace chemical contaminants within each chert type’s resulting XRD spectrum. Reflectance infrared data were then collected on larger, whole samples of chert, and transmission infrared data were collected on the powdered samples. The same trace chemical contaminants identified in the XRD data were then sought in the infrared spectra. In reflectance mode, one sample of each chert type was analyzed in the same spot multiple times so that tiny peaks could be distinguished from background noise. Reflectance and transmission infrared spectra of common mineral contaminants (hematite, calcite, pyrite, etc.) were also obtained and compared to the infrared spectra of the four chert types. GRAMS/AI – Thermo Scientific software was used to examine each infrared spectrum. This data will be used to evaluate whether reflectance infrared microspectroscopy can be useful for determining the provenance of chert artifacts.