PIMA Spectroscopy PIMA PROJECT

Below is a description of a one-year project. This material is based upon work supported by the National Science Foundation under Grant No. 9971179. The principal investigator is Sarah Wisseman, Director of ATAM, with co-principal investigators Thomas Emerson, Illinois Transportation Archaeological Research Program and Anthropology; Randall Hughes, Illinois State Geological Survey; and Duane Moore, Illinois State Geological Survey.

A central problem in archaeology is the accurate and cost-effective sourcing of materials in order to understand patterns of raw material procurement, artifact production, and redistribution. Archaeometric data are then used to explore the nature and extent of cultural interaction and influence between contemporary cultures. The focus of this project is North American stone artifacts from two periods, Middle Woodland and Middle Mississippian, that appear to represent maxima in patterns of the geographical extent and intensity of material exchange. Although considerable archaeometric work has already been performed on Hopewellian materials such as metals, shell, cherts, ceramics, and meteoric iron, more limited research has been conducted on Middle Mississippian artifacts and, until recently, Cahokia "red goddess" stone figurines and Hopewellian pipestone effigy pipes had not been examined. At the University of Illinois, X-ray diffraction (XRD) and sequential acid dissolution-inductively coupled plasma (SDA-ICP) analyses have narrowed the sources of Cahokian figurines from Arkansas, Minnesota, or Missouri to local Missouri flint clays. This result has forced the reexamination of exotic material use at Cahokia since earlier theories suggested that the Cahokia elite obtained their stone from much farther south. Similarly, the same techniques have been used on Hopewellian pipes, artifacts traditionally believed to have been produced in and distributed from Ohio across the Midwest. Instead, some of the Hopewell pipes recovered in Illinois were manufactured out of local flint clays from northwestern Illinois. The limiting factor in research to date has been the destructive nature of the techniques, which cannot be applied to most museum artifacts. Significant numbers of Hopewellian pipes and Cahokia figurines are held in museum collections, with predictable limitations on sampling.

In this project, we propose to test the field and museum use of a PIMA® (Portable Infrared Mineral Analyzer) spectrometer that is portable, non-destructive, and rapid. The PIMA provides mineralogical analyses of rock chips, thin sections, or whole artifacts and complements other techniques such as XRD and ICP. We expect that the PIMA® spectrometer will prove its usefulness as a cost-effective, non-destructive means of mineralogical characterization for a wide variety of archaeological and geological materials. Preliminary research has demonstrated the value of mineralogical methods in addition to elemental analyses, first because they provide a set of data that give geological information beyond simple numbers, and second because earth materials with similar chemical compositions contain mineralogical suites that are often quite distinctive. The PIMA® will be especially useful to field archaeologists who need rapid mineralogical assessment of plausible stone and clay sources which in turn will give them better discrimination of which areas should be sampled for further mineralogical and elemental analyses. In the museum setting, the PIMA® will make it possible to characterize stone and clay materials non-destructively and add to already existing archaeological and geological databases on the sources of valuable Midwestern materials.

The primary tasks for this pilot project are:

1. PIMA® analyses of pipestone (flint clay) samples and related mineral reference standards that have been or will be analyzed by XRD;
2. PIMA® analyses of additional pipestone samples, where small sample size and large number of samples precludes XRD or other types of analyses;
3. PIMA® analyses of a pipestone artifacts in museums and private collections, only a few dozen of which could be sampled and analyzed by XRD.

Copyright 2000. University of Illinois at Urbana-Champaign.