Julio pokes his head up from the vertical shaft just ahead. “No force,” he says into the dark. “No muscle.”I stop wriggling, close my eyes, try to relax into the mountain. My breath reluctantly returns. I slither forward cautiously, reverently. Somehow my arms come free, and I’m able to pull myself through. My panic subsides. The Cerro has released me.

Bolivia is perpetually gripped by social conflict, having suffered more than 188 coups d’état since its founding, in 1825, by the father of Latin American rebellion, Simón Bolívar. The constitutional crisis raging outside is fuelled by the same cultural and socio-economic divisions that have defined Bolivian life and politics for centuries. On one side are the poor, indigenous majority of Quechua, Aymara, Chiquitano, and Guarani campesinos, factory workers, and miners for whom Pachamama, or Mother Earth, is a sacred deity. On the other are the relatively prosperous right-wing mestizo elite, of mixed European and Indian descent, who pray to the distinctly more secular god of market capitalism. Until now, either the mestizo or the military has essentially ruled Bolivia since the Spanish left.

This profound rift is apparent even in the nation’s geography. Bolivia is divided by South America’s two most significant topographical features: the Andean mountain range in the west, where most Indians live and where Potosí and La Paz, both Morales strongholds, are located; and the resource-rich Amazon rainforest in the east, home mainly to mestizos and that bastion of anti-Morales sentiment, the wealthy jungle city of Santa Cruz, which is responsible for an estimated 45 percent of Bolivia’s economy.

The meetings of the constituent assembly charged with drafting the constitution were proving a most theatrical forum for this divide. Rife with controversy since its formation in 2006, spiked with overt racism on both sides, and stricken by months-long debates over voting rules and at least one rollicking fist fight, the assembly had polarized the country more profoundly than any mountain range or economic philosophy ever could.

Morales, whose mas party held 137 of the 255 seats, envisioned that the new constitution would redistribute the nation’s wealth more equitably. mas planned to nationalize Bolivia’s oil and gas sectors, cap land ownership at 10,000 hectares, and replace the Senate with a body that better represented the country’s indigenous majority, including the miners. Opponents of mas, led by podemos, the nation’s Santa Cruz–based right-wing party, held just sixty seats. They were crusading to maintain the neo-liberal status quo of freewheeling foreign investment and private ownership, and to shift more control over natural resource revenues away from La Paz and into the hands of local elites.

Although mas failed to win the two-thirds majority required to control the assembly, the new constitution was expected to follow the party’s prescription. And so we had the violence of Black November. The white-walled city of Sucre in flames. High-heeled women, men in business suits, and right-wing youth groups rampaging through the streets. At least 100 prisoners escaping the San Roque Jail. At least three demonstrators shot dead. Bolivia, in the view of many, on the verge of civil war — the Andean Wiphala flag versus the Spanish Cross.

For good reason, constitutional issues in Bolivia are routinely couched in the rhetoric of a centuries-old culture clash. But as the miners of Potosí know all too well, the schisms here are fuelled by something more fundamental than race or creed. After all, the eastern lowlands aren’t just home to the mestizos. They also host enormous deposits of natural gas, South America’s second-largest reserves behind Venezuela’s. It is the allocation of this bottomless bank account, tops on a long list of mineral riches, that the people of Bolivia are really fighting over.

On the fourth level of La Negra, we find Julio at a fork in the shaft, perched on a pile of blasted stone. He is laughing with three edgy young Quechuans. This is the drilling team. Their mandate: open a set of twelve holes in the wall around the corner. These will later be packed with dynamite. The men are clothed, as are we, in the ubiquitous uniform of the Cerro Rico miner: hooded full-body overalls, black rubber boots, hard hat, headlamp, and an overcoat of ghostly grey dust. They are following a vein of zinc to the east.

One of the men wears an additional piece of equipment over his nose and mouth: an old-school half-face filter mask. At his feet lies a hulking mass of rusted machinery, an ancient pneumatic jackhammer with a chisel the width of my wrist affixed to its end.

“This man is expert driller,” says Julio.