Investigation of a simulated Chinese jade and bronze dagger-axe by neutron radiography and prompt gamma activation analysis

Abstract In ancient China during the Shang dynasty, ca. 1600 BCE–1046 BCE, intricate jade and bronze dagger-axes ( ge ) were made and used by the elite as ritual symbols of power and prestige. These meticulously crafted ceremonial weapons consist of a nephrite jade [Ca 2 (Mg, Fe) 5 Si 8 O 22 (OH) 2 ] blade mounted in a bronze haft. Several examples of these dagger-axes are included in collections in the United States. There has been recent interest in applying neutron radiography to image the jade tang hidden within the bronze haft and uncover early manufacturing techniques. As a preliminary test of feasibility, a simulated dagger was made using a modern replica blade carved from nephrite from Wyoming, USA, and copper alloy plates. The simulated dagger was first imaged by X-ray and neutron radiography at the NIST Neutron Imaging Facility. The details of the jade tang within the copper alloy haft were clearly visible. Subsequently, the nephrite blade and the copper alloy plates were analyzed by cold prompt gamma neutron activation (PGAA) to evaluate the feasibility of this technique for identifying the nephrite source. The PGAA was performed at the Cold Neutron PGAA station at NIST. Three nephrite specimens in the Smithsonian collection from China, Siberia and Taiwan, characterized previously by electron microprobe analysis, were used as comparative standards. The major nephrite elements - Ca, Mg, Fe and Si - were analyzed with uncertainties in the range of 0.3%–0.4%. Three of the trace elements conventionally used for sourcing, Cr, Mn and Ni, were analyzed with similar uncertainties. The residual radioactivity of the objects was below the NRC exempt limits.