LA-ICP-MS analysis of corroded glass beads from Southern China: tackling highly inhomogeneous archaeological glass

Abstract

ABSTRACT Excavated glass artifacts are usually environmentally impacted, causing spatial inhomogeneity which poses great challenges for accurate and non-destructive chemical characterization. Here, we present our study on accurate characterization of archaeological glass with Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), a high-precision and minimally destructive analytic method. Using three corroded glass beads excavated from Guangnan, Yunnan, Southern China as examples, we discuss the issues that may be involved when observing signal curves of highly inhomogeneous archaeological glass, as well as provide chemical characterization for the intact pristine body. Results indicate that these Indo-Pacific monochrome beads are of the potassium silicate glass type and used mineral potash source, and that they contain copper as the colorant. By discussing the breadth and depth types of inhomogeneity and focusing on perturbation endured by major elements, we identify the extent of environmental alteration and describe how different elements and matrices can respond differently to the archaeological environment, leading to various corrosion behaviors. For such samples LA-ICP-MS is shown to be an advantageous tool to provide archaeologically relevant information, or to probe artifact conditions for conservation purposes. A good understanding of sample conditions, and close attention to the experimental and calibration process are required to overcome inhomogeneity when tackling archaeological glass.