In 1545 the Spanish conquerors discovered a huge silver deposit in a mountain in the Bolivian Andes they then dubbed Cerro Rico (Rich Hill). Over the course of the next centuries most of the silver was extracted through an elaborate system of forced labour imposed on the indigenous population, called the 'mita', as well as flat-out forced labour by African slaves.
The workers spent periods of weeks or months inside the shafts without seeing daylight. They kept themselves going by chewing coca leaves, which sedate feelings of exhaustion and hunger and raise spirit and awareness. They nonetheless died by the thousands.

The city created at the foot of Cerro Rico, Potosí, became home to both the mine-owners and to huge numbers of mine labourers and their families. For almost a century Potosi accounted for more than half of all the silver entering Europe from the New World, causing economic boomtimes in the Old World. Potosí at its hight was a city on par with Madrid and Paris, with nearly 150.000 inhabitants, full of palaces and cathedrals in the central area, and rundown slumtowns nearer Cerro Rico itself.

Today the palaces and colonial riches can still be seen in the city center. The part of town near Cerro Rico is still a slumtown providing shelter to the miners. Small cooperatives manually scrape the last bits of silver and tin from the shafts created in colonial times.
Breaking the stone and getting the rubble out is hard physical labour. The miners strain their bodies to the maximum by eating little food and chewing lots of coca. Conditions inside the mines are unhealthy, to say the least: aside from poison fumes and lack of oxygen, there's the dust from dynamiting done to break loose parts of the veins.
The miners on average live to the age of 40. When a miner dies his sons usually start work in the mines to earn the family income. Which means you'll see kids of 10 years old and up working inside the shafts. The miners widow sometimes earns part of the income too, by going through the piles of left-over rubble outside the mines looking for forgotten bits of silver or tin.

The motive to work a job with such a high level of mortality is both a socially ingrained and a financial one. It's passed down from father to son, from generation to generation. The miners earn wages slightly higher than farmers working in the altiplano. And if a miner manages to save just enough to buy a concession on part of the hill and finds a good vein there, he'll have his fortune made. He can bring in other miners to do the work for him and at some point he himself can retire from the mine.
All miners hold weekly ritual offerings of coca leaves and pure alcohol to their devil-god Tio in order to humour him enough to one day find such a vein.