A visit to the Cooperative Mines will almost surely be one of the most memorable experiences you'll have in Bolivia, providing an opportunity to witness working conditions that are among the most grueling imaginable. You may be left stunned and/or ill.In the cooperative mines on Cerro Rico, all work is done with primitive tools, and underground temperatures vary from below freezing - the altitude is over 4200m - to a stifling 45°C on the fourth and fifth levels.

Miners, exposed to all sorts of noxious chemicals and gases, normally die of silicosis pneumonia within 10 to 15 years of entering the mines.

Contrary to popular rumor, women are admitted to many cooperative mines; only a few miners hang on to the tradition that women underground invite bad luck, and in many cases, the taboo applies only to miners' wives, whose presence in the mines would invite jealousy from Pachamama. At any rate, lots of Quechua women are consigned to picking through the tailings, gleaning small amounts of minerals that may have been missed.

Since cooperative mines are owned by the miners themselves, they must produce to make their meager living. All work is done by hand with explosives and tools they must purchase themselves, including the acetylene lamps used to detect pockets of deadly carbon monoxide gas.

Miners prepare for their workday by socializing and chewing coca for several hours, beginning work at about 10:00. They work until lunch at 14:00, when they rest and chew more coca. For those who don't spend the night working, the day usually ends at 19:00. On the weekend, each miner sells his week's production to the buyer for as high a price as he can negotiate.

When miners first enter the mine, they offer propitiation at the shrine of the miners' god Tata Kaj'chu, whom they hope will afford them protection in the harsh underground world. Deeper in the mine, visitors will undoubtedly see a small, devilish figure occupying a small niche somewhere along the passageways. As most of the miners believe in a god in heaven, they deduce that there must also be a devil beneath the earth in a place where it's hot and uncomfortable. Since hell (according to the traditional description of the place) must not be far from the environment in which they work, they reason that the devil himself must own the minerals they're dynamiting and digging out of the earth. In order to appease this character, whom they call Tío (Uncle) or Supay - never Diablo - they set up a little ceramic figurine in a place of honor.

On Friday nights a cha'lla is offered to invoke his goodwill and protection. A little alcohol is poured on the ground before the statue, lighted cigarettes are placed in his mouth and coca leaves are laid out within easy reach. Then, as in most Bolivian celebrations, the miners smoke, chew coca and proceed to drink themselves unconscious. While this is all taken very seriously, it also provides a bit of diversion from an extremely harsh existence. It's interesting that offerings to Jesus Christ are only made at the point where the miners can first see the outside daylight.

In most cooperative operations there is a minimal medical plan in case of accident or silicosis (which is inevitable after seven to 10 years working underground) and a pension of about around US$15 a month for those so incapacitated. Once a miner has lost 50% of his lung capacity to silicosis, he may retire, if he so wishes. In case of death, a miner's widow and children collect this pension.

Dozens of Potosí operators offer guided tours through the mines. The best tour guides tend to be ex-miners, who know the conditions and are friendly with the men at work.

Mine visits aren't easy, and the low ceilings and steep, muddy passageways are best visited in your worst clothes. You'll feel both cold and hot at times, there will likely be a bit of crawling through narrow shafts, and the altitude can be extremely taxing. On some tours, you'll end up walking three or four kilometers inside the mountain. You'll be exposed to noxious chemicals and gases, including silica dust (the cause of silicosis), arsenic gas, and acetylene vapors, as well as asbestos deposits and the byproducts of acetylene combustion and the detonation of explosives. Anyone with doubts or medical problems should avoid these tours. The plus side is that you can speak with the friendly miners, who will share their insights and opinions about their difficult lot. It's not a zoo; the miners are proud of their work in such tough conditions, and generally very happy for visitors to observe their toil.

Tours begin with a visit to the miners' market, where miners stock up on acetylene rocks, dynamite, cigarettes and other essentials. In the past, gifts weren't expected, but with the growing number of tourists through the mines, you'd be very unpopular if you didn't supply a handful of coca leaves and a few cigarettes - luxuries for which the miners' meager earnings are scarcely sufficient. Photography is permitted. The tours then generally visit an ingenio, before heading up to the Cerro Rico itself. There's often a demonstration of a dynamite explosion; the force is like a hammer blow to the chest even at some distance.

Mine tours run in the morning or afternoon and last from three to six hours; you tend to get longer in the mine on the morning visits. The standard charge is around US$10 per person; lower rates may be available during periods of low demand. This price includes a guide, transportation from town and equipment: jackets, helmets, boots and lamps. Wear sturdy clothing and carry plenty of water and a handkerchief/headscarf to filter some of the noxious substances you'll encounter underground. There is less activity in the mines on Saturdays, Sundays and Mondays. The last Friday of the month can be a particularly eventful day and is recommended for those with a taste for hard liquor.