Different shades, various metals: A multianalytical investigation on Iranian copper-based artifacts (7th–14th century CE) from the Metropolitan Museum of Art

A group of copper-based artifacts in the collection of the Metropolitan Museum of Art, lacking clear archaeological provenance, has been attributed to early and pre-modern Islamic Iran based on their stylistic features and forms. To gain insight into the materials and metalworking techniques used in their production, these artifacts were subjected to microanalytical investigation. A non-invasive micro-XRF technique was employed to characterize the alloy composition of the artifacts and their decorative inlays. Additionally, the microstructure of a selected group of artifacts was examined using scanning electron microscopy–energy dispersive X-ray spectroscopy, and metallography techniques. The results revealed that the artifacts were produced with a range of copper-based alloys, including leaded ternary (Cu-Zn-Sn-Pb), high-tin bronze, and brass. The inlays consisted of silver (alloyed with copper), impure copper, and alloyed gold. The leaded ternary artifacts exhibited a cored cast microstructure with evidence of cold-working and numerous large lead globules, while the tin bronze and brass artifacts displayed signs of the thermo-mechanical operations used to shape them. Based on these findings, Iranian copper-based metalworking in the Islamic period is shown to have employed a variety of compositions as well as a range of shaping and decorative techniques.