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Micro- and Nanoscale Surface Analysis of Late Iron Age Glass from Broborg, a Vitrified Swedish Hillfort

Published

Author(s)

Bethany Matthews, James Neeway, Lorena Nava Farias, Jose Marcial, Bruce Arey, Jennifer Soltis, LiBor Kovarik, Zihua Zhu, Michael Schweiger, Nathan Canfield, Tamas Varga, Mark Bowden, Jamie Weaver, John McCloy, Rolf Sjoblom, Eva Hjärthner-Holdar, Mia Englund, Erik Ogenhall, Edward Vicenzi, Claire Corkhill, Clare Thorpe, Russell Hand, David Peeler, Carolyn Pearce, Albert Kruger

Abstract

Archaeological glasses with prolonged exposure to biogeochemical processes in the environment can be used to understand glass alteration, which is important for the safe disposal of vitrified nuclear waste. Samples of mafic and felsic glasses with different chemistries, formed from melting amphibolitic and granitoid rocks, were obtained from Broborg, a Swedish Iron Age hillfort. Glasses were excavated from the top of the hillfort wall and from the wall interior. A detailed microscopic, spectroscopic, and diffraction study of surficial textures and chemistries were conducted on these glasses. Felsic glass chemistry was uniform, with a smooth surface showing limited chemical alteration (<150 nm), irrespective of the position in the wall. Mafic glass was heterogeneous, with pyroxene, spinel, feldspar, and quartz crystals in the glassy matrix. Mafic glass surfaces in contact with topsoil were rougher than those within the wall and had carbon-rich material consistent with microbial colonization. Limited evidence for chemical or physical alteration of mafic glass was found; the thin melt film that coated all exposed surfaces remained intact, despite exposure to hydraulically unsaturated conditions, topsoil, and associated microbiome for over 1,500 years. This supports the assumption that aluminosilicate nuclear waste glasses will have a high chemical durability in near-surface disposal facilities.
Citation
Microscopy and Microanalysis

Keywords

Glass, micro-analysis, durability, archaeometry, resilience

Citation

Matthews, B. , Neeway, J. , Nava Farias, L. , Marcial, J. , Arey, B. , Soltis, J. , Kovarik, L. , Zhu, Z. , Schweiger, M. , Canfield, N. , Varga, T. , Bowden, M. , Weaver, J. , McCloy, J. , Sjoblom, R. , Hjarthner-Holdar, E. , Englund, M. , Ogenhall, E. , Vicenzi, E. , Corkhill, C. , Thorpe, C. , Hand, R. , Peeler, D. , Pearce, C. and Kruger, A. (2023), Micro- and Nanoscale Surface Analysis of Late Iron Age Glass from Broborg, a Vitrified Swedish Hillfort, Microscopy and Microanalysis, [online], https://doi.org/10.1093/micmic/ozac032, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933279 (Accessed May 25, 2024)

Issues

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Created January 11, 2023, Updated March 1, 2023