A major silver lode at Cerro Rico was discovered in 1545, catalyzing the rapid growth of Potosí into a mining settlement whose output would become central to Spanish imperial finance.
In the first decades after 1545, silver was largely produced from near-surface ores using Indigenous wind-drafted smelting furnaces (often described as guayras/huayras). This phase depended heavily on Indigenous mining and metallurgical labor before deeper ores forced technological change.
Bartolomé de Medina developed (and scaled) the patio process, using mercury amalgamation to extract silver from lower-grade ores—an innovation that later underpinned Potosí’s revival once rich oxidized ores were depleted.
Colonial cinnabar mining and refining at Huancavelica began in the mid-1560s, creating a critical regional mercury supply that enabled large-scale amalgamation refining in the Andes (including Potosí).
Viceroy Francisco de Toledo visited Potosí in 1572 and pursued reforms to stabilize extraction, taxation, and administration—key steps in consolidating the mining complex, the town, and the labor system that supplied it.
Under Toledo’s expanded colonial mit’a (a coerced labor draft), the first recruits arrived in Potosí in 1573, institutionalizing large-scale Indigenous compulsory mine labor and reshaping Andean communities through long-distance labor obligations.
With Andean mercury supplies available, Potosí adopted mercury-amalgamation refining in the early 1570s (with sources commonly placing full adoption by 1574). This shift made lower-grade ores profitable and sharply increased both refining capacity and labor demands.
A royal mint (Casa de Moneda) was established at Potosí in the early 1570s; records cited by numismatic historians indicate that the first silver coinage from the new mint began on 1574-03-28, strengthening imperial control over silver flows and taxation.
Potosí’s refining complex increasingly depended on hydraulic power (reservoirs, canals, and mills/ingenios) to grind ore for amalgamation. This infrastructure helped make Potosí one of the world’s largest 16th-century industrial complexes and intensified coerced labor in and around the city.
Factional conflict among Spaniards in Upper Peru—closely tied to competition over access to mining offices and profits—erupted into violence in Potosí and surrounding mining regions from 1622 to 1625, illustrating how silver wealth shaped local politics and insecurity.
On 1626-03-15, the San Ildefonso dam burst and flooded Potosí, destroying many ore-processing plants (ingenios) and causing severe economic losses and deaths. The disaster underscored the vulnerability of the silver economy to failures in its hydraulic infrastructure.
In 1649 a major scandal over debased coinage erupted at the Potosí mint, with investigations confirming short fineness in widely circulating silver coins. The episode damaged trust in currency and disrupted trade far beyond the Andes.
In October 1650, Philip IV ordered devaluation of 8- and 4-real coins amid the Potosí mint fraud crisis, a policy that affected Potosí-origin currency broadly and reflected the global monetary reach of Andean silver.
The 1780–1781 cycle of rebellion associated with Túpac Amaru II (and connected uprisings across the southern Andes) amplified challenges to colonial exactions, including labor drafts and tribute systems that fed mining centers such as Potosí.
Late-18th-century Bourbon administrative reforms expanded the intendancy system in the southern Andes and adjacent jurisdictions (including Charcas/Upper Peru), reshaping fiscal administration closely tied to mining revenues and regional governance.
Studies of colonial refining estimate that mercury vapor emissions from Potosí’s silver refining remained substantial through the late colonial period (1574–1810), reflecting the long-run scale of amalgamation and its severe health and environmental impacts on workers and residents.
Potosí silver mining boom and labor regimes (1545–1800)
