Microanalytical Confirmation of Surface Patination and Silicate Cementation in Carved White Jade Figurines of the Warring States Period (475–221 BCE)

This study presents a carved white jade figurine from the Chinese Warring States period (475–221 BCE), characterized by distinct reddish-brown surface patination and stylistic carving consistent with the period. Using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), we identified a cemented quartz–aluminosilicate sand grain, firmly integrated into a recess of the carving and bound by iron oxide films. The analysis confirms that the coloration and cementation result from long-term burial processes. The morphological features of patination, microstructural data, and the absence of modern contaminants strongly support the authenticity and ancient origin of the object. Keywords: jade, Warring States, patina, SEM-EDS, authenticity, burial processesКлючевые слова (中文): 玉 (yù), 战国 (Zhànguó), 包浆 (bāojiāng), 鉴定 (jiàndìng) Introduction The Warring States period (475–221 BCE) is known for highly sophisticated jade carving, where symbolic animal and dragon figures reflect both ritual and decorative functions. Authentic jades from this era exhibit not only stylistic markers in carving but also natural surface transformations — patination and infiltration of soil particles — resulting from centuries of burial. This study documents a carved white jade figurine with winged dragon motifs, showing reddish patina and a sand grain cemented in a carved recess. The goal is to provide microanalytical confirmation of natural burial processes that support the authenticity and ancient origin of the artifact. Materials and Methods Object: White nephrite figurine, private collection (attribution: Warring States, 475–221 BCE). Macroscopic analysis: Optical examination of carving lines, patina distribution, and stylistic motifs. SEM-EDS: Conducted at 15 kV, spot analysis of cemented grain and surrounding patinated surface. Elements analyzed: Si, O, Al, Fe, Mg, Ca, K, Na, Sr, S. Documentation: Photomicrographs of surface patina and cemented inclusions. Results 1. Carving and stylistic features The figurine demonstrates motifs typical of the Warring States period: abstracted dragon body, geometric wing pattern, drilled perforations, and spiral motifs. Carving lines show differential polish, consistent with ancient working tools. 2. Surface patination Reddish-brown iron oxide patina distributed along recesses, forming capillary meniscus patterns. “Orange-peel” island-like spots characteristic of Fe-oxide precipitation. Differential thickness: thinner on ridges, thicker in recesses, bridging over micro-chips. 3. SEM-EDS microanalysis Quartz–aluminosilicate matrix: Si 9–17 at.%, O 41–51 at.%, Al 3–11 at.%. Iron oxides: Fe up to 34 at.% in localized regions. Minor phases: Mg 1–7 at.%, Ca 1–2 at.%, K/Na 1–3 at.%, Sr ~0.5 at.%, S up to 2%. Interpretation: natural sand grain cemented to jade surface by Fe-oxide films, consistent with burial in silicate-rich soil environment. Discussion The patina morphology and EDS results confirm that the reddish coloration derives from natural Fe-oxide deposition during burial, not artificial staining. The cemented grain is securely integrated into the patinated surface, a feature impossible to reproduce by modern enhancement. These results align with previous studies of weathering processes in archaeological jades, where iron oxides form stable crusts and cement soil particles. The stylistic and material evidence together confirm the attribution of the object to the Warring States period. Conclusion The jade figurine exhibits authentic carving style and motifs characteristic of the Warring States period. Natural Fe-oxide patination and cemented quartz–aluminosilicate grain confirm prolonged burial. Microanalytical data provide independent evidence for authenticity and ancient origin. References Taube, K. (2000). The symbolic role of jade in ancient China. Antiquity. Liu, Y., et al. (2021). Mineralogical characteristics of burial alteration on Chinese jades. Journal of Archaeological Science. Zhao, Y., & Wang, C. (2019). Iron oxide patination in ancient nephrite: processes and diagnostics. Heritage Science. Zhang, H. (2017). Weathering crusts on jade artifacts from the Warring States period. Archaeometry. Hou, X., et al. (2021). Provenance and microstructural analysis of jade artifacts from early China. Scientific Reports. Formation of Ferruginous Patina and Sand Cementation on Jade Surfaces Step 1. Burial Environment The jade object is buried in soil or river sediments rich in silica (SiO₂) and iron-bearing minerals. Groundwater circulates through pores and carved recesses of the jade surface. Step 2. Iron Mobilization Iron is released from soil minerals (e.g., Fe-bearing clays, feldspars, or ferromagnesian minerals). In reducing conditions Fe²⁺ is soluble and transported by groundwater. Step 3. Oxidation and Precipitation When groundwater contacts oxygenated microenvironments near the jade surface, Fe²⁺ oxidizes to Fe³⁺. Fe³⁺ hydrolyzes and precipitates as iron (oxyhydr)oxides: goethite (α-FeO(OH)), hematite (Fe₂O₃), or ferrihydrite. These precipitates form thin reddish-brown films (patina) on the jade surface. Step 4. Capillary Deposition Fe-oxide gels accumulate preferentially in carved recesses and microcracks. Capillary forces concentrate the iron-rich solutions along incision lines, producing meniscus-like deposits. Step 5. Sand Grain Incorporation Detrital sand grains (quartz, feldspars, aluminosilicates) are transported by soil water and trapped in the surface cavities. Fe-oxide gels precipitate around these grains, acting as a natural cement. Over time, the grains become firmly bound to the jade surface. Step 6. Long-term Transformation Continued burial stabilizes the patina: amorphous Fe-oxyhydroxides transform into crystalline goethite or hematite. The patina becomes inseparable from the jade surface, and sand grains remain “glued” in place, serving as micro-archives of the burial environment.