Iron Mineralization of Textiles from Iron Age Burial Sites in Slovenia

Ancient textiles made of natural materials, such as cellulosic and protein-based fibers, are rarely preserved in archeological contexts, unless specific conditions are met that would contribute to their preservation. Such conditions include direct contact with metals, eventually creating fiber casts—produced by mineralization—that could survive for thousands of years. Mineralization from contact with iron has been well documented, though poorly studied and understood in comparison to copper mineralization. Additionally, iron has been known to primarily create negative casts, which are imprints of the individual fibers, rather than positive casts, which are the result of the natural fibers being replaced by the mineral formed from the metal oxide. The samples used for this thesis are of iron mineralized textiles from Iron Age inhumation burial sites in Slovenia, spanning from the 8th to 4th century BC, and were mostly determined to be wool fibers from previous research. The current thesis’ goal is to understand why some of these fibers were mineralized as positive casts rather than negative and to better understand as to how this may have occurred. The methods for archaeometric analysis include: (1) scanning electron microscopy (SEM), (2) SEM-Energy Dispersive Spectroscopy (SEM-EDS), (3) micro-Raman, and (4) Fourier-Transform Infrared spectroscopy. Initial analysis of SEM-EDS showed that both the positive casts and negative casts were indeed iron oxides. Further analysis using micro-Raman and FTIR has been explored to determine the specific iron oxide formed to better deduce the mineralization pathway of the iron metal with the textiles under the burial conditions. In order to ensure a better understanding of the possible burial conditions, an extensive literature review has been carried out on the geography and soil morphology of Slovenia to contextualize what would be expected pH levels and moisture content of the soil. This allows the preliminary understanding that the acidic levels of the soil and presence of water possibly contributed to the rapid formation of positive casts in some of the samples, especially since iron is not biocidal and would not be naturally able to deter degradation of the textiles from microbial and fungal activity.