R1: Characterization and description of minerals (Joint Session with The Gemmological Society of Japan)

[R1P-05] Mineralogical and chemical features of tiny bronze fragments from the Yashin Tepe archaeological site, northeastern Iraq

*Masanori KUROSAWA¹, Kei Ikehata¹, Shin'ichi Nishiyama² (1. Univ. Tsukuba, 2. Chubu Univ.)

Keywords:bronzeware, corrosion, chemical analysis, copper isotope, Neo Assyria

Tiny corroded bronze fragments, excavated from the Neo-Assyrian Yashin Tepe site at northeastern Iraq, were analyzed with SEM-EDS, Raman microprobe, ICP-MS, and MC-ICP-MS to elucidate original chemical features of bronzewares distributed in the eastern border of the Neo Assyrian Empire. The bronze fragments, tens micron to a 1 mm in sizes, were mainly covered with malachite on the surface, and inside there was tin-copper alloy with patches of pure-copper separated. A thin film of copper sulfate and tiny particles of lead chloride were often observed under the surface layer of malachite. The tin-copper alloy with little corrosion was a low-tin bronze with low lead content, could corresponding to a chemical composition of original bronzeware related to the bronze fragments. In addition, the composition was almost the same as those of the bronze products excavated from the Nimrud site, capital of Neo-Assyria, implying strong ties between the capital and the border. The bronze fragments also contained almost no impurities such as As, Sb, Ni, and Bi. Copper isotopic ratios (delta⁶⁵Cu) of the fragments ranged from -0.83‰ to 0.57‰. Both features were consistent with those of the copper materials that were widely distributed during the Neo-Assyrian period.