Microscopic characteristics and weathering mechanism of pigment layers in Huashan Rock Art, Guangxi, China

Huashan Rock Art, located in Guangxi, China, reflects the social, economic, cultural, and artistic aspects of the local ancestors and is included in the World Cultural Heritage list. However, surface cracking and pigment layer detachment have severely affected its value. This study employed Scanning Electron Microscopy (SEM), micro X-ray fluorescence (μ-XRF), micro-Raman, and X-Ray Diffraction (XRD) to analyze the micro-characteristics of the rock art’s surface. Results show a three-layer surface structure: calcium sulfate, pigment layer, and rock layer. Calcium sulfate is partially embedded into the pigment layer, making it difficult to remove. The distribution of calcium sulfate indicates that sulfur (S) mainly comes from the external environment. XRD analysis reveals that the phase changes of calcium sulfate play a significant role in rock art deterioration. This study provides a new microscopic perspective for pigment layer research and offers a scientific reference for the protection and study of rock art heritage.