Influence of surface roughness on the spectroscopic characterization of jadeite and greenstones archaeological artifacts: The axe-god pendants case study

This research addresses a critical methodological challenge in archaeological spectroscopy by investigating how surface topography affects the non-invasive characterization of jadeite and greenstone artifacts. Using 45 geological samples from Guatemala’s Motagua Fault Zone and 12 axe-god pendants from Costa Rican museums, the study demonstrates that infrared, Raman, and X-ray fluorescence spectra are strongly influenced by surface roughness parameters, particularly arithmetic average height (Ra) values. The research reveals significant spectral changes including 13-21 cm⁻¹ shifts, 17-87% intensity reductions, and complete band loss in samples with higher roughness values. For the first time in archaeological spectroscopy, the study applies Functional Data Analysis (FDA) to treat spectra as continuous functions rather than discrete data points, providing more appropriate statistical treatment for spectroscopic data. The findings establish that FT-IR spectroscopy is most suitable for portable field studies despite roughness effects, while recommending analysis on surfaces with Ra < 1.05 μm for optimal results. This work provides essential methodological guidelines for the reliable spectroscopic characterization of archaeological materials while preserving artifact integrity.

Recommended citation: Hernández-Murillo, C., García-Piedra, S., Alfaro-Córdoba, M., Fernández-Esquivel, P., Ménager, M., & Montero, M. L. (2022). "Influence of surface roughness on the spectroscopic characterization of jadeite and greenstones archaeological artifacts: The axe-god pendants case study." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 267: 120508.
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