The implication of varying 14C concentrations in carbon samples extracted from Mongolian iron objects of the Mongol period

Accelerator mass spectrometric (AMS) radiocarbon measurements were performed with carbon samples extracted from cast iron and steel artifacts excavated in the 13th to 14th century Karakorum site of the Mongol period. The 14C levels in most specimens were too low to represent the real age of the given artifacts, particularly in cast iron objects, whose 14C concentrations were negligible. This discrepancy was much less pronounced in steel objects, but still quite significant. One notable exception was found, however, in a steel artifact whose radiocarbon date was consistent with its known age. These AMS data suggest that mineral coal was employed primarily for the smelting of cast iron while charcoal served as the major source of fuel for other iron and steelmaking processes. This can explain the significant variation in 14C concentrations for steel products that were fabricated by treating cast iron in a charcoal-fired environment, as confirmed in some of the artifacts examined. This variation may have important archaeological applications in characterizing technological transitions associated with the use of fossil fuels in preindustrial iron industry.