Arsenic

The arsenic in all the Gawra copper-based artifacts in this study most likely derive from the original copper ore, its variation (from near-trace levels to around 2.2%) simply reflecting differences in the conditions of smelting of the original copper ore. 

Level VIII:
Range: 0.17%­1.0% (n=4)
Mean: 0.73% ± 0.19% (1 standard error) 

Level VII:
Range: 0.11%­2.1% (n=16)
Mean: 0.93% ± 0.12% (1 standard error) 

Level VI:
Range: 0.04%­2.2% (n=74)
Mean: 0.87% ± 0.05% (1 standard error)

Level V:
Range: 0.21%­1.6% (n=12)
Mean: 0.76% ± 0.12% (1 standard error)

Level IV:
Range: 0.08%­1.6% (n=4)
Mean: 0.60% ± 0.36% (1 standard error)

Not included in these statistics, however, is the exceptionally high As-level (12.5%) measured for the Stag’s head (inv. 31-52-270) from Level VI. This may be an instance of a deliberate addition of arsenic, so that the object would have a silvery-white appearance. This artifact is too small to allow the taking of a metallographic section, so there is no way of knowing whether the richness in arsenic is only superficial, and perhaps artificially induced. If that were to be so, this Stag’s head would have a well-studied parallel in a bronze bull from the site of Horoztepe (northeastern Turkey), that dates to around 2100 B.C. (see Smith 1973).