The forgotten framework: analysis of organic residues on Bronze Harness Ornaments of Shang and Western Zhou Dynasties unearthed at Xitou site in Shaanxi, China

To examine the form of harnesses from the Shang and Western Zhou dynasties (16th–8th century B.C.) in China, this study analyzed the black-brown granular and thin-striped organic residues found on the bronze 韅 (Xian, a leather belt around a horse’s abdomen) ornaments unearthed from the Shangmiao Cemetery of Xitou Site in Xunyi (Shaanxi, China). The residues were investigated by microscope, scanning electron microscopy (SEM), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), and Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS). The results revealed that the microstructure of the residues closely resembled leather relics, and infrared analysis indicated that the residues contained proteins, confirming their identification as leather. Further analysis by ZooMS (Zooarchaeology by Mass Spectrometry) confirmed the leather to be Bovini (Bos) hide. This suggests that the use of Bovini hide as a material for making Xian was well established during the Shang and Zhou periods. The leather likely served to connect the various parts of the harness and fasten it to the horse for use. This study marks the first research of Xian from these periods in China. The residues have survived attributed to the bactericidal effect of copper ions on the surface of the bronze Xian ornaments and the potential mineralization of the leather. Additionally, peculiar curly green bundles found within the residues are hypothesized to be related to the formation of copper soap or curly malachite.