Comparative Analysis of Trace Element Spatial Distribution in Freshwater and Seawater Pearls

The spatial distribution of trace elements (Mn, Sr, S, and P) in freshwater and seawater pearls was systematically investigated using micro‐X‐ray fluorescence (micro‐XRF) mapping combined with ultraviolet–visible–near infrared (UV–Vis–NIR) reflectance spectroscopy, Raman spectroscopy, and energy‐dispersive X‐ray fluorescence (EDXRF) spectroscopy. Results revealed distinct concentric Mn/Sr‐enriched spherical zones in the nacreous layer of freshwater pearls, with 3–4 zones in non‐nucleated pearls and 2–3 zones in nucleated ones. In contrast, seawater pearls exhibited uniform Sr‐ distribution without concentric enrichment patterns. Notably, Mn and Sr co‐enriched zones were consistently observed in all studied freshwater pearls, regardless of nucleation status. Furthermore, S and P exhibited homogeneous distributions in freshwater and seawater pearls. It is preliminarily considered that the concentric Mn/Sr‐ co‐enrichment patterns in freshwater pearls are attributed to environmental fluctuations, such as temperature variations and nutrient availability. The thickness of individual enriched zones and the spacing between adjacent zones may be a record of mineralization rates, indicating environmental changes during cultivation. In contrast, the stable marine environment of seawater pearls should result in uniform Sr distribution, with minimal Mn incorporation. These findings advance our knowledge of the biomineralization mechanisms of pearls and the gemological distinctions between freshwater and seawater pearls. More importantly, this work not only establishes diagnostic criteria for pearl origin identification, but also offers preliminary insights into the potential environmental implications of pearl cultivation, which may inspire further research into its role in water quality management and ecological restoration.