NIST - National Institute of Standards and Technology

08/05/2026 | Press release | Archived content

Methods for Estimating Fe Redox in Mesoamerican Jadeite Jade

Published
August 5, 2026

Author(s)

Edward P. Vicenzi, Thomas Lam, Evan Jahrman, Bruce Ravel, Melinda Dyar, Jamie Weaver

Abstract

Green jadeite has been selectively mined and used by Mesoamerican Indigenous cultures for centuries, with the green hues resulting from interactions among various chromophores, including Cr3+, Fe3+, and Fe2+. This study employed Fe K-edge X-ray absorption near-edge structure (XANES) measurements using a mm-scale X-ray beam to estimate the iron-redox ratio in jadeitite, with scanning electron imaging and X-ray microanalysis employed to determine mineral compositions and proportions within the synchrotron analysis zones. Results for the XANES measurements were processed using two distinct approaches based on different underlying assumptions: peak fitting and machine learning. Despite their differences, both peak fitting and machine learning approaches yielded statistically consistent results, suggesting that the analysis assumptions were valid for this system and that XANES data can provide reliable Fe redox estimates for jadeites. The Fe3+/FeTotal range for the jadeites measured by XANES was estimated to be between 75% and 91% after accounting for phase mixing (omphacite with jadeite) within samples. Low Fe concentrations in jadeites precluded the use of quantitative compositional analysis to estimate Fe redox using the charge balance method.
Citation
American Mineralogist
Pub Type
Journals

Keywords

Iron speciation, XANES, Morimoto, Cultural Heritage, Machine Learning, greenstone, X-ray absorption spectroscopy

Citation

Vicenzi, E. , Lam, T. , Jahrman, E. , Ravel, B. , Dyar, M. and Weaver, J. (2026), Methods for Estimating Fe Redox in Mesoamerican Jadeite Jade, American Mineralogist, [online], https://doi.org/10.2138/am-2025-10045, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958788 (Accessed August 11, 2026)
Additional citation formats

Issues

If you have any questions about this publication or are having problems accessing it, please contact [email protected].

NIST - National Institute of Standards and Technology published this content on August 05, 2026, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on August 11, 2026 at 09:24 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]