Arsenic

The arsenic in all the Kish copper-based artifacts in this study most likely derive from the original copper ore, its variation (from near-trace levels to around 4.0%) simply reflecting differences in the conditions of smelting of the original copper ore. 

ED I: 
Range: 0.31%–4.0% (n=13) 
Mean: 1.73% ± 0.33% (1 standard error) 
Highest As-level: Flat adze (inv. FM158 182)

ED III/Akk: 
Range: 0.051%–4.0% (n=43) 
Mean: 1.53% ± 0.15% (1 standard error) 
Highest Sn-level: Pin (inv. FM228 473)