Origin characteristics of Ming-Qing inscriptionless blue bricks via K-means analysis

Provenancing ancient Chinese blue bricks—essential to UNESCO sites like the Great Wall—is hindered by the absence of restoration records and illegible inscriptions. This study introduces a k-means-based parallel analysis approach integrating X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses to particularly trace inscriptionless bricks. Applied to 42 Ming-Qing inscriptionless samples, this method clustered samples based on regions with significant differences in XRD patterns and the element composition detected by XRF. Furthermore, based on the two clustering results, we plotted a cross-matrix diagram to discuss the characteristic differences between XRF and XRD in bricks detection. Finally, we identified four typical characteristics of ancient blue bricks from unlabeled samples by correlating firing temperature and elemental concentration. The consistent clustering results suggested shared material sources between Mingzhongdu and Mount Wudang bricks. This method provides an effective solution for determining origins of inscriptionless bricks, advancing architectural history research and heritage conservation practices.