mount cerro, mine tour

It is from Potos� that most of the silver shipped through the Spanish Main came. According to official records, 45,000 tons of pure silver were mined from Cerro Rico from 1556 to 1783. Of this total, 9,000 tons went to the Spanish monarchy. Indian laborers, forced by Francisco de Toledo, Count of Oropesa through the traditional Incan mita institution of contributed labor, came to die by the thousands, not simply from exposure and brutal labor, but by mercury poisoning: in the patio process the silver-ore, having been crushed to powder by hydraulic machinery, was cold-mixed with mercury and trodden to an amalgam by the native workers with their bare feet. The mercury was then driven off by heating, producing deadly vapors.