Micro-Raman spectroscopy and complementary techniques for the study of iron weapons from Motya and Lilybaeum (Sicily, Italy): Corrosion patterns in lagoon-like and calcarenitic hypogea environments

Micro-Raman spectroscopy (mu-RS) has been used to characterize mineralogical phases of corroded iron materials, buried in lagoon-like and calcarenitic hypogea environments. A set of samples from the Phoenician site of Motya (8(th)-6(th) centuries BC, Sicily) and from the Punic Necropolis of Lilybaeum (4(th) century BC, Sicily) were analyzed combining mu-RS with scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) and high-resolution field emission scanning electron microscopy (HR-FESEM). Micro-Raman results revealed the presence of magnetite, goethite, lepidocrocite, and hematite as the main corrosion products and soil minerals as quartz, calcite, barite, actinolite, microcline, zircon, and Ti-oxides. SEM and HR-FESEM allowed exploring micro- and sub-micrometer structures of iron oxy-hydroxides though sections from rim to core. The different corrosion models suggest polymorphic inter-conversions among iron oxy-hydroxides and dissolution-re-precipitation reactions. In addition, the occurrence of magnetite and metal core that survived in armors buried in the hypogea site of Lilybaeum indicates more stable environmental conditions than those of Motya.