Cinnabar in Mesoamerica: poisoning or mortuary ritual?

Abstract In Mesoamerica, dead bodies were often smeared with red pigment, either hematite or cinnabar. Most archaeological remains include bones whose surface may be red colored. Being cinnabar a mercury compound whose chemical formula is HgS, it is not clear if Hg ions diffuse into the hydroxyapatite lattice. In this work we found that cinnabar is not easily dissociated and, therefore, ions from cinnabar spread after death, if any, do not diffuse into hydroxyapatite. However, in bones from the archaeological site of Ranas, close to Queretaro, Mexico, we found Hg ions in interstitial positions of the bone hydroxyapatite lattice. Ranas was a cinnabar mining zone. Hence, the presence of Hg ions in bone hydroxyapatite lattice cannot be due to post mortem rituals and it has to be attributed to breathing or swallowing of mercury vapors or solutions during life. It is, then, a case of poisoning with mercury, probably due to exposition to vapors originated in the mine exploitation or to contaminated food.