PIMA SPECTROSCOPY PIMA SPECTROSCOPY

The PIMA is a shoebox-sized, portable infrared spectrometer that can be used for qualitative identification of the minerals in stone and low-fired clay artifacts. The instrument can be operated in the field or in a museum setting, and the analysis is totally non-destructive. PIMA requires no sample preparation and leaves no radiation damage. The PIMA window is held up against the flat surface of an artifact and the reading takes only 30-60 seconds, allowing the rapid collection of a large number of analyses. Measurements can be made on whole or partial artifacts, potsherds, rock chips, powders, and soil samples. PIMA spectroscopy uses the short wavelength infrared (SWIR) part of the electromagnetic spectrum (from 1300-2500 nanometers) and measures the reflected radiation from the surface of a sample. This measurement reveals the interatomic bond energies characteristic of specific minerals. 

The PIMA has been used successfully by geologists in the U.S., South America, Australia, and Europe for mineral exploration, studying the degree of crystallinity of minerals, and mapping alteration systems. Its immediate application to archaeology is in sourcing of stone and clay artifacts, providing another analytical tool to supplement and complement more costly and destructive techniques such as X-ray diffraction (XRD).

PIMA analysis works best on minerals that contain hydroxyls (OH groups) such as phyllosilicates (including clay, chlorite and serpentine minerals), hydroxylated silicates (such as epidotes and amphiboles), sulphates (alunite, jarosite and gypsum) and carbonates. Dehydrated materials such as high-fired ceramics do not produce useable spectra (low-fired ceramics may work, but this has yet to be determined). 

The PIMA technology is expected to be most useful in providing mineral composition for museum artifacts that cannot be destructively sampled and in identifying potential sources of clay and stone in the field that can then be sampled for additional laboratory testing.

*We are currently using a PIMA SP, purchased from Integrated Spectronics Pty Ltd, Australia. For more information, see the PIMA SP web page.

Spectra courtesy of Integrated Spectronics Pty Ltd.

This material is based upon work supported by the National Science Foundation under Grant nos. 9971179 and 0203010. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation

Copyright 2000. University of Illinois at Urbana-Champaign.