Mercury source in Copan (Honduras): Local mining or trade?

Mercury was widely used in the art and rituals of the pre-Columbian Maya. A large amount (> 6 kg) of documented liquid mercury has been recovered in Maya cultural deposits at Copan, Honduras. The Copan Acropolis also contains abundant evidence of cinnabar (mercury sulfide) use in ritual practice: sprinkled over tomb surfaces; coating the bones of the dead; and covering offerings. Discovering the specific source of cinnabar and liquid mercury used in Copan will contribute to further interpretations of economic networks utilized by the Copan Maya. The geology of the Copan Valley supports the hypothesis that mercury could be mined locally. To test it we designed a geochemical survey on the stream network within the Copan watershed basin using portable X-ray Fluorescence Spectrometry (pXRF) analysis. Results of the survey confirmed data from previous geologic mapping, indicating the presence of mercury in the valley. However, its concentrations are extremely low, sporadic and do not support its potential as a mining source. Therefore, it is very likely that mercury found in Copan ritual contexts was brought from elsewhere either as tribute or through trading.