A Study on Composition and Manufacturing method of Bronze Pins from Dia ardizi Moorani Iron Age site, Luristan

Luristan, located in west of Iran, is an important region in the field of metallurgy of the Iron Age in Iran, but comparing to its huge bronze finds or attributed to it, there is little information about the metallurgical technology in this area. Dia ardizi Moorani is one of the prehistorical sites which is excavated recently in southern Luristan. According to the various finds, such as a number of architectural structures, debris of the six grave stone, a burial, pottery, stone, bone, metal etc., during one excavation season, a settlement from chalcolithic to Iron Age has been observed in this area. A significant number of bronze objects are among the findings of this site. Therefore, to recognize the ancient metallurgical technology in the site, seven bronze pins belong to Iron Age were studied using laboratory method including metallography and scanning electron microscopy coipled with energy dispersive X-ray spectroscopy (SEM-EDS) in order to identify chemical composition and manufacturing techniques. The results of SEM-EDS showed that except for one sample made of arsenic copper alloy, all of the pins were made of tin bronze with different amount of tin which indicates the method of producing bronze alloy without control on tin amount similar to other areas of Iron Age in Iran. SEM-EDS analyses also revealed elements such as nickel, silver, arsenic and iron as minor elements in all samples which could be attributed to the impurities of the ore used in the metal extraction process. In addition, microstructural investigation clearly showed various sulfide inclusions and lead globules. Moreover, elongated inclusions can be an indication of significant hot working or cold working and annealing to achieve the final shape. Also, the microstructures of the pins revealed re-crystallized twin grain structures that indicate the use of multiple procedures, including hot-working or cold-working and annealing to manufacture these pins.