Nondestructive identification of a jet bead from the Changle Cemetery in Ningxia, China

Some bright black beads with dense surface and poor light transmittance are generally considered as jet artifacts in China. However, little scientific investigation has been applied to support this judgment. This study focuses on the nondestructive identification of a jet bead, unearthed from the Changle Cemetery, Han Dynasty (202 BC-AD 220), Ningxia, China through multi nondestructive approach. The results of Gas Chromatography-Mass Spectrometry (GC/MS) analysis indicate that the bead belongs to coal products, based on the typical coal biomarkers including n-alkanes, acyclic isoprenoids and terpenoids. FTIR analysis further confirms that the bead is made of jet in comparison with modern jet samples in China. The bead is also scanned with Synchrotron Radiation Micro-computed Tomography (SR-μCT) to obtain the structure and drilling technology information, which suggests that the bead is uniform and was drilled from both sides. The nondestructive identification of ancient jet artifacts is first reported in China up to date, which not only reveals the varied utilizations of coal products in ancient society but also suggests that the popularization of jet in the Han Dynasty might be related to the first large-scale exploitation of coal, and offers an effective method suitable for archaeological jet samples.