Technical Studies on Two Copper-Based Objects from the Bronze Age of Iran

A multianalytical study was undertaken on two copper-based objects from northern Iran that are dated to the Late Chalcolithic and Bronze Age including an arm ring from Tappeh Hissar and a dagger from Tureng Tepe. The study was performed by using chemical and microscopic methods including inductively coupled plasma-optical emission spectroscopy (ICP-OES), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and optical microscopy (metallography). The results showed that the dagger has been made of tin bronze alloy while the arm ring is made of impure copper with a low amount of arsenic. Both objects are shaped and manufactured by cycles of cold-working and annealing although it has not been enough in the arm ring to remove all coring occurred during the casting. This is recognizable by the fact that super-imposed microstructure in the form of partially parallel banded “ghost” microstructure is visible in the etched cross section of this object. The non-metallic inclusions are scattered in the microstructure of the objects. They can be identified as sulphidic copper inclusions in the dagger and oxidic copper inclusions in the arm ring. This shows the use of different copper ores to produce these objects. Consequently, it can be assumed that two objects were manufactured and produced by two different processes even though both were common production and working techniques during the Late Chalcolithic and Bronze Age on the Iranian Plateau.