It’s pitch black as we squat down in the swelteringly hot, dank mine shaft, 800 metres underground.
The sound of hurried footsteps and panting break our nervous silence.
“Put your fingers in your ears,” Choco screeches, with a disconcerting tone of uncharacteristic aggressiveness.
We wait as the miner makes repeated clicking sounds with his mouth, seemingly counting down.
Then he says “Now!”
Before I hear it, I feel it. The most powerful sensation I’ve ever experienced.
The solid natural rock walls and roof vibrate so vigorously that for a moment I actually wonder if the mountain is going to collapse in on itself.
Then comes the noise.
A thunderous roar that cuts through the finger earplugs and makes my heart beat like a pneumatic drill.
Then it’s over.
“That’s just one stick of dynamite,” says Choco. “Normally I blow up 60 in one go.”
This guy’s got bigger balls than a nymphomaniac in an isolation chamber.
He is one of 15,000 miners who slog it out for shifts of up to an eyelid-drooping 24 hours straight in what is hailed the Planet’s most dangerous mine, in the World’s highest city – Potosí, Bolivia.
More than eight million people have lost their lives in the frightening darkness of the unstable underground shafts that criss-cross their way through the huge mountain of Cerro Rico.
Everywhere there are dangers and I am relieved to have been kitted out with a helmet, because as I walk with a stoop along the low corridors I repeatedly smack my head against the jagged rock above me.
Intermittently I hear loud snake-like hisses coming from the tubes that pump pressurised air deep into the mountain, to power the miners’ expensive diamond-tipped drills.
“Don’t touch this,” says Choco, pointing to yellow stalegtites descending from the cave roof like icicles. “Arsenic. Poison. Dead.”
He’s a main of few words, but in this instance no more is needed. The point is made and fully understood.
Below us our feet slosh about in water so filthy that Choco says it would spell the end if you drank it.
Crawling on hands and knees up narrow passages, our guide, who is leading the way, regularly shouts “Guarda!”(“Watch out!”).
It is a warning that he has just stepped on a loose bit of rock that is now freewheeling its way towards us.
Finally the shaft opens out and three miners greet us like long lost friends.
Each has a Popeye-sized cheek full of coca leaves (the raw material used for making cocaine). This ubiquitous miners’ foodstuff is normally all they eat for a whole day. It is used to help stave off hunger, to maintain energy levels and to stay alert.
However, it quickly emerges that my new amigos have been mixing their coca consumption with a considerable quantity of alcohol – 96 per cent proof sugarcane spirit, or ‘whisky’ as it is known in these parts – and they are all more than a little worse for wear.
“It’s Monday. Monday is drinking day,” says Choco. Although considerably less work takes place on the first day of the week, miners still descend into the black depths and attempt to dig out minerals while heavily under the influence.
Before entering the darkness, we had stopped at the miners’ market to buy gifts for the workers.
Along with my first ever purchase of a stick of dynamite (complete with detonator, fuse and ammonium nitrate to give it an extra ‘bang’) I’d also bought heavy duty gloves, coca leaves and super-strong whisky and peach juice.
I hand over my gifts to a jovial big-bellied miner called Pablo.
In his first few sentences, he tells me he has been working down the mine since he was 12 years old and that he has only ever loved one woman, with whom he has ten children.
Next, that he is 51 now but will be dead before he reaches the age of 55 because of the build up of dust in his lungs, which will cause a condition called silicosis.
“Why don’t you stop now, can’t your children look after you?” I ask.
He flashes a wry smile. “I am working here so they don’t have to. Besides, it is too late. I will die down here. Soon.”
Pausing for the faintest of moments, he snaps back to the here and now.
“A drink please, señor.” I offer him my bottles of whisky and peach cordial. He mixes up a potent cocktail and pours a triple shot into a cup cut from a plastic bottle.
In his right hand (for good luck) he tips a bit of liquid onto the pile of rocks to his side for Pachamama (Mother Earth, the female god outside the mountain), a little more for El Tio (the underground devil, the male inside the mountain) and a final dribble for Las Almitas (the souls of departed friends).
The bottle then gets passed around our small group and, as the person who enjoys the last tipple, it falls on me to make up a new concoction and I begin another round.
Pablo begins “talking to El Tio” as he drifts off to sleep and his son Ivan, 19, shows us how to separate the rock bits according to quality: first class, silver; second, zinc; third, tin. He tells us he has been grafting down the mine since he was 14 years old, to support himself through a university degree.
“It’s difficult working here, very difficult,” he says, as his dad mumbles to the devil a few metres away. “I remember my first time in here and I was terrified. But the mine becomes like a second home and the other miners are like your family.
“Each day when you leave your mother and father and siblings, you always have to say “Adiós” (Goodbye), not “Hasta luego” (See you soon), because you never know if you will see them again. I have lost two friends in the mine.”
Afterwards, the third member of the group, Tuki, demonstrates the technique for chiselling out rock from the “vein” they are following in the hope of finding pure silver. He tells us the story of the mine.
In 1985 the government cut funding for mining in the mountain because the price of the minerals dropped. As a result local cooperatives sprang up.
Today there are 48 cooperatives in Potosí mine, with about 18 groups in each cooperative – a minimum of three miners in each group.
Although miners now earn more money, there are no rules or regulations. If they get injured, they receive no help and they get no pension. They work as hard as they want to work.
Millions of slaves died after the conquistadors first discovered the mines of Cerro Rico. They plundered as much of the precious metal as they could. Slavery is no more, but today the risks are still huge. In Pablo’s cooperative alone, 20 people have died since 1952. Just five days ago, three miners were killed as they tried to place dynamite into dug-out holes in the wall.
They are long, hard days for the miners, who work either 6, 12 or 24-hour shifts depending on how much of the mineral is being discovered in the seam they are exploiting.
The most dangerous part of the job is, not surprisingly, dealing with dynamite. I’m amazed I am able to just roll up to a street stall and buy the stuff.
Choco shows us the bomb-making process, folding up the squidgy stick and putting it in a plastic bag containing tiny pink balls of ammonium nitrate.
He carefully attaches the metal detonator and the gunpowder-filled fuse.
To light the dynamite he uses small peeled bits of gunpowder fuse, called banana sticks he says using a lighter would not give him enough escape time. Once ignited he sprints to a spot 80 metres away and then ‘boom!’
That night, Choco invites us for a drink in one of the miners’ bars in the city centre.
“Did you enjoy it?” he asks.
“A thousand times more authentic than the mining tours you get in Britain,” I tell him.
“Oh, what we saw today was a slightly less dangerous area of the mine,” he says.
I’d love to experience the dodgy part.