text: Strong evidence of metallurgical activities has been revealed in levels 9 to 6, dating to the Ubaid period, and especially in level 7 (4166 +/- 170 cal BC). Hearths or natural draft furnaces, slag, ore, and pigment had been recovered throughout the site. This was in the context of architectural complexes typical of southern Mesopotamian architecture.
  Unusually, the metallurgical activities at the site appear to have been limited to the melting and casting of copper objects. Arsenical copper objects were clearly manufactured on site, yet the technological aspects of this productions remain unclear. This is because the primary smelting of ore seems to have been undertaken elsewhere, perhaps already at the mining sites. So questions remain as to whether or not arsenic was already present in the ores, or added later.
  In contrast, the related Norşuntepe site provides a better context of production, and demonstrates that some form of arsenic alloying was indeed taking place by the 4th millennium BC. Since the slag identified at Norşuntepe contains no arsenic, this means that arsenic was added separately.