Rust Condition of Ironware Unearthed from Tombs of the Sixteen Kingdoms in Guanzhong

Two typical artifacts, an iron mirror and an iron knife, unearthed from the tombs of the Sixteen Kingdoms in Guanzhong, Shaanxi were taken as the research objects. A portable hyperspectral spectrometer (HS) was used to identify the different colors of rust on the surface of iron objects in situ and non-destructively. The morphology, structure and composition of different rust products were finely identified by optical microscopy, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and micro-confocal Raman spectroscopy. The results showed that the composition of rust products of different colors was significantly different. Among them, the black rust product was mainly magnetite, and the brown rust product was composed of various products such as goethite, lepidocrocite and hematite. Its also revealed that in an alkaline soil environment, Ca²⁺, HCO^3-, Cl^- and the acidification of iron bacteria jointly affected the formation process of goethite and calcium carbonate sediments.