Structural study of archaic orichalcum ingots from gela (sicily) via time-of-flight neutron diffraction

Abstract Orichalcum is a precious copper-zinc alloy known from ancient Mediterranean contexts. Eighty ingots of Orichalcum were recovered underwater near Gela (Sicily, Italy) and they are dated back to the 6th century BCE establishing a unicum in the Mediterranean Sea. Here, 11 selected representative ingots were studied via Time-of-Flight Neutron Diffraction (ToF-ND) to investigate microstructure. This approach allows the analysis of the bulk ingot studying structure, phase composition, strain and texture in non-invasive and non-destructive technique. The obtained phases composition and the microstructure results suggest that the ingots were prepared by roughly controlling the thermic parameters of the casting procedure furthermore the microstructural parameters highlight difference between distinct families of ingots. The results provide new information on the bulk microstructure and metallurgical processing of these ancient ingots, demonstrating the potential of ToF-ND as a non-destructive tool for the archaeometallurgical investigation of complete archaeological metal objects.