In 1545, Spanish colonists began exploiting a major silver deposit at Cerro Rico, near what became the city of Potosí (in present-day Bolivia). The discovery quickly turned a high-altitude settlement into a strategic mining center for the Spanish Empire and a major driver of global silver supplies.
In the first decades after 1545, miners focused on unusually rich, near-surface silver ores that could be processed with relatively simple smelting. This early phase helped finance rapid urban growth, but it also began patterns of high labor demand and dangerous working conditions.
In the 1550s, Bartolomé de Medina developed the patio process, which used mercury to pull silver from crushed ore. This innovation mattered because it made it profitable to process lower-grade ores, extending the life of silver districts once the richest ores were exhausted.
By the 1560s, mercury (needed for amalgamation) was produced on a large scale at Huancavelica in Peru, creating a linked system: mercury from Huancavelica enabled silver refining at Potosí. This connection increased production capacity but also introduced major mercury exposure risks for workers and surrounding communities.
In 1572, a royal mint was founded in Potosí to turn silver into coin and bullion for imperial finance and trade. Minting linked forced labor in the mines to global money flows by converting extracted metal into widely used currency.
Viceroy Francisco de Toledo visited Potosí in 1572 and reorganized mining and labor systems to increase output and tighten Crown control. A key shift was the formal expansion of the mining mita—mandatory rotational labor drafts imposed on Indigenous communities—which helped secure a steady workforce for mines and refineries.
By the late 1570s and around 1580, the patio method and water-powered milling infrastructure were implemented at large scale in Potosí. This industrial system allowed lower-grade ore to be processed in high volumes, helping drive Potosí’s peak production era.
On 1626-03-15, the San Ildefonso dam burst, flooding Potosí and destroying many ore-processing plants (ingenios). The disaster disrupted production and highlighted how dependent silver refining was on water infrastructure for powering mills and moving ore and slurry.
In 1649, a major scandal revealed that some Potosí coins were debased (made with less silver than required), undermining confidence in silver money circulating far beyond the Andes. The investigations and reforms that followed show how mining, refining, and state oversight were tightly connected—and how corruption could damage imperial finances.
By the 1600s, Potosí had grown into a huge mining and processing center with extensive reservoirs, aqueducts, and ore mills. UNESCO describes a workforce that included thousands of Indigenous people compelled to work under mita, showing how urban growth depended on coercive labor systems.
After the late 1600s boom, production faced growing problems: richer veins were depleted, deeper mining became more expensive, and labor shortages increased as Indigenous populations fell due to disease and exploitation. These pressures reduced output and made the forced-labor system even more contested and unstable.
In the mid-1700s, the Spanish Bourbon monarchy pursued reforms aimed at raising revenue and boosting productivity, including measures affecting mining finance, mercury pricing, and taxes. These efforts sought to sustain silver output but also increased tensions by reshaping burdens on Andean communities and regional economies.
Beginning in 1780, the Túpac Amaru II rebellion spread across parts of the southern Andes, fueled by opposition to intensified colonial demands under Bourbon-era policies. The rebellion explicitly targeted abuses linked to systems like the mining mita, signaling that coerced labor and heavy taxation were central political flashpoints in the late colonial economy.
By around 1800, the pace of mining and processing at Potosí slowed significantly compared with earlier centuries. The long arc from discovery to decline shows a system built on industrial-scale infrastructure and forced labor—and how depletion, disasters, and political conflict gradually limited the model’s ability to sustain high output.
Potosí Silver Mining and Forced Labor Systems in the Andes (1545–1800)