In colonial times, the Spanish mined an enormous amount of silver from Potosí using slave labor in four month shifts. By this I mean that the slaves stayed underground for four months at a time. The silver mined here was one of the major sources of funding for the Spanish empire. Now all that's left are the scraps.
The mines here are now collectives, meaning they are owned by the miners themselves. Actually, they are technically owned by the government and leased to the mining collective. To become a member of the collective, a miner must work for three years, pay a fee, and find an area of his own to mine. There are fewer and fewer veins left and they tend to be evermore deep, requiring work in extreme heat, up to 45C, and extra labor to get the minerals to the surface.
We went on a tour of one of the mines and it was eye opening. I had been in an abandoned mine before, but never one full of workers. Due to the particulates in the air and the fumes from dynamite, miners lose a large portion of their lung capacity after a decade or so, many die young of silicosis pneumonia, and most only live into their fifties. Despite all this, they all seemed to be in good spirits and enjoyed the camaraderie of working in close knit groups. At one point, we helped the miners furiously shovel rocks into huge buckets to be winched up and I only lasted three buckets before having to take a break, but they shovel nonstop for hours everyday. After only 20 minutes below the surface, and before even touching a shovel, I was exhausted and had neck pain from having to walk hunched over while looking forward at the same time. I can't imagine spending eight to ten hours a day down there, six days a week. Tragically, these guys don't have many other options.