What is FTIR?

Fourier-Transform Infrared Spectroscopy (FTIR) is a non-destructive analytical method that examines how a material absorbs infrared light across different wavelengths. Each mineral has a unique absorption pattern, or “spectral fingerprint,” that reflects its crystal structure and chemical bonds. By analysing these spectra, FTIR makes it possible to distinguish between raw materials that appear visually similar, such as jadeitite, nephrite, and serpentinite. The method can be applied directly to an artefact surfaces without damaging the object, and produces reliable mineralogical identifications even on highly polished tools.

Application in FROM STONE TO HOME

We apply FTIR to both polished stone tools and geological samples collected from field surveys at procurement sites. The method allows us to confirm mineral identifications and to detect subtle differences between related rock types that can be overlooked through visual or microscopic analysis. By comparing artefacts with geological samples, FTIR helps us establish reference spectra for known sources. These reference datasets then serve as a comparative baseline for evaluating the provenance of archaeological artefacts across the Aegean.

Workflow

Samples are analysed using an FTIR spectrometer that measures how infrared light is absorbed at molecular bond levels. For polished stone tools, measurements are made directly on the artefact surface. Geological samples collected in the field are also measured, creating a comparative spectral library. The spectral data are then processed, standardised, and integrated into the project’s open database. FTIR results are cross-referenced with pXRF elemental profiles and LA-ICP-MS trace element and isotopic data, providing a multi-dimensional perspective on raw material characterisation and provenance.

Challenges and Solutions

One challenge of FTIR is that surface conditions, such as weathering or patination, may interfere with spectral measurements. To reduce these effects, we use multiple readings from different areas of the artefact and compare the results against unweathered geological samples.

Outcome

FTIR offers a precise way to distinguish between visually similar stone types and to confirm mineral identifications. When combined with pXRF and LA-ICP-MS, FTIR strengthens our ability to establish provenance baselines and to trace the origins of polished stone tools. As part of FROM STONE TO HOME, this method is crucial for understanding the mineral variability of raw materials and for linking artefacts to their geological sources, helping to reconstruct resource procurement and exchange networks of the past.