Colonial ruins at Huancavelica, Peru, are reminders of the harsh conditions local miners endured under Spanish rule.

Cave-ins and mercury poisoning were rampant and helped earn the main mine the nickname Mina de la Muerte (Mine of Death).

Radiocarbon dates suggest that by 1450, as the Incas were expanding their reach, cinnabar smelting generated gaseous mercury, according to the May 2009 study. That would have been more toxic than the cinnabar dust that resulted from earlier efforts to produce vermilion pigment.