The Spanish mine owners weren’t necessarily overtly abusive to the indigenous workers. They didn’t have to be; the conditions in the mines were enough to kill the hardiest workers.

Colonial miners worked, ate, and even slept in the mines. They were beasts of burden, carrying the heavy mineral in huge sacks on their backs. They were constantly exposed to hazards: collapsing shafts, exposure to mercury, asbestos and other airborne particles, wet, cold conditions, malnutrition, and extremely rigorous work.

Accurate estimates on the total number of people that died during the 252-year reign of the mita system are difficult to come by. I have heard estimates as high as 8 million, which is equal to the entire current population of Bolivia and represents eighty per cent of the male population of the 16 provinces of the viceroyalty of Peru.

Legend says that the mines had two adjacent entrances, one in which the mitayos would enter, and another where their dead bodies were carried out.  All Bolivian school children are well versed in a tragic metaphor: using all of the mineral extracts from Potosi, a bridge of pure silver could be built from Bolivia to Spain, and another bridge back again to Bolivia using the bones of the Indians who died in the mines.

Even today the Bolivian miners live short, brutal lives. Silicosis, a respiratory disease caused by the inhalation of airborne particles, and accidents kill the majority of miners by the age of 40.

The use of coca was extremely important in the mines of Potosi, and remains so today. Initially, the Spanish associated the Indian custom of chewing coca as a devilish, pagan practice, and it was promptly outlawed by colonial authorities.

The Spanish soon realized, however, that when indigenous laborers chewed coca they performed their tasks more dutifully, and were able to concentrate for longer periods of time with less fatigue. Coca also suppressed hunger and thirst. In light of these discoveries, the crown quickly revoked its ban on coca, and massive amounts of the plant were cultivated in the tropical regions and brought to Potosi by llama train to supply the ever-increasing demand.

Enormous amounts of corn were also brought from the temperate valleys for the production of chicha, an alcoholic beverage common in the Andes. These agricultural products and others were transported great distances on beasts of burden: mules, donkeys, horses, and of course, llamas. The entire colonial economy of Upper Peru revolved around the axis of Potosi, the gem of the world.