Silver mines throughout history were worked overwhelmingly by enslaved people and forced laborers. In ancient Greece, enslaved men extracted ore by hand in the Laurion mines near Athens. In colonial South America, millions of Indigenous people and enslaved Africans were compelled to work the massive silver deposits at Potosí and other sites. By the 19th century, immigrant wage laborers took on the dangerous work of industrial silver mining in places like Nevada. The story of silver mining is, at every stage, a story of coerced or marginalized labor.
Enslaved Workers in Ancient Greece
The silver mines at Laurion, about 40 miles south of Athens, powered the economy of classical Greece. Ore was extracted manually by skilled individuals, and the vast majority of them were enslaved. The workers who processed ore in treatment workshops above ground were also predominantly slaves, meaning that Athenian wealth was largely built on enslaved labor.
The total number of people forced to work at Laurion is uncertain, but the ancient historian Thucydides recorded that 20,000 enslaved workers fled the mines during the Peloponnesian War in the late 5th century BCE. That number suggests the actual workforce was even larger during peak production. These workers labored in narrow, suffocating tunnels carved into rock, often crawling through shafts barely wide enough for a human body. The silver they produced funded Athens’ navy, its public buildings, and its political influence across the Mediterranean.
Forced Indigenous Labor at Potosí
When Spanish colonizers discovered the massive silver deposits at Cerro Rico in present-day Bolivia in 1545, they needed an enormous labor force to exploit them. Viceroy Francisco de Toledo formalized the solution in the 1570s: the mita, a system of compulsory labor that drafted Indigenous peasants from 16 provinces across Upper Peru. Workers were forced into the dark, deepening mine shafts for minimal wages, rotating through grueling shifts that could last days underground without surfacing.
The mita became so dreaded that communities made extraordinary sacrifices to escape it. By the mid-1600s, buying an exemption cost around 150 pesos per person. By 1660, Indigenous communities were collectively paying roughly 587,000 pesos per year just to keep their people out of the mines. Those who couldn’t pay had no choice. The system persisted for nearly two centuries, and some estimates place the total death toll at Potosí as high as eight million people, including both Indigenous workers and enslaved Africans who were also forced into the mines.
Enslaved Africans in Colonial Mines
Indigenous workers were not the only forced laborers in Spain’s silver economy. Enslaved African people were brought to mines across South America and Mexico, where mine owners faced strict economic obligations and constant demand for more labor. In Mexico, mine operators relied on a combination of enslaved Africans and Indigenous workers who were pressured or coerced into service. The gold and silver mines that Spain erected throughout the Americas were, as the Library of Congress describes them, “rife with abuse and mistreatment” of both groups.
The precise number of enslaved Africans in silver mining is harder to pin down than the mita figures, partly because colonial records tracked them differently. But their presence was significant enough to shape the demographics of mining towns across the continent.
Mercury Poisoning and Its Toll
Beyond the physical dangers of collapsing tunnels and crushing labor, silver refining exposed workers and their families to mercury, which was used to separate silver from raw ore. The health consequences were devastating and well documented even at the time. Writing around 1590, the Jesuit priest José de Acosta described how workers who inhaled mercury vapor during the refining process “get mercury poisoning and die, or remain in a very bad state or lose their teeth.”
In 1629, the priest Pedro de Oñate wrote of witnessing firsthand “how terrible are the effects of mercury” on workers involved in smelting and processing. It wasn’t only the men who worked directly with the metal. Their families often helped prepare, operate, and clean the mercury ovens. Mercury crosses the placental barrier, putting unborn children at risk of developmental abnormalities. An 18th-century chronicler of Potosí made frequent references to birth deformities, stillbirths, and mental illness in the mining community. The city also gained a reputation for aggressive behavior among its residents, a pattern consistent with chronic mercury exposure. The contamination from centuries of refining still affects residents of Potosí and the mercury-producing town of Huancavelica today.
Women’s Roles Above Ground
Women were largely excluded from underground extraction, but their labor was essential to silver production. In Zacatecas, Mexico, one of New Spain’s major silver districts, Indigenous women performed a wide range of work that kept mining operations and communities running between the 1620s and 1770s. They prepared and distributed food and goods at mining haciendas, managed small-scale trade and market activities, and maintained properties in the city.
Their contributions went beyond support work. Indigenous women migrated to Zacatecas in large numbers, settling there even during periods when silver output declined. When male workers were absent for long stretches, which happened frequently in mining towns, women ran households and managed community affairs. As primary caretakers, they also used legal channels to protect their children from the abusive labor practices common in mining districts. Historians have argued that these roles above ground were as vital to the silver economy as the extraction work performed underground.
Immigrant Laborers in the American West
By the 19th century, silver mining shifted partly to wage labor, though conditions remained brutal. The Comstock Lode, discovered in Nevada in 1859, drew workers from around the world. Irish, Cornish, Chinese, and Mexican immigrants made up much of the workforce. Chinese workers, who came to represent about 10 percent of Virginia City’s population, called Nevada “Yin Shan,” meaning Silver Mountain, distinguishing it from “Gum San,” or Gold Mountain, their name for California. Census records from 1870 show Chinese residents working as miners, laborers, merchants, cooks, and laundrymen.
Industrial mining brought new hazards. Underground temperatures in the Comstock tunnels could exceed 120°F, and miners worked in shifts of only 15 to 30 minutes before needing to cool down. Silicosis, a lung disease caused by inhaling rock dust, became a major killer. A study of nearly 10,000 white male metal miners in the United States found that those who developed silicosis had a 73 percent higher rate of lung cancer death compared to the general population. Even miners without a silicosis diagnosis faced elevated lung cancer risk. These diseases often took years to develop, meaning miners didn’t realize the damage until long after their working years.
The workforce of silver mines, across thousands of years and multiple continents, was composed almost entirely of people who had little or no choice in the matter: enslaved people in ancient Athens, conscripted Indigenous communities and enslaved Africans in colonial South America, and immigrant laborers with few alternatives in the industrial era. The silver that built empires and filled treasuries was extracted at extraordinary human cost.