Mining Our Past
A Comparison of Peruvian Silver Refineries with West Virginia Coal Mines
​Image Above: A drawing by Peter Schimidtmeyer from 1824 depicting a Peruvian silver and copper refinery. The image includes a mill with a water-powered wheel, furnaces, men treading on ore within a patio, and women washing and bagging ore at the end of the patio process. Courtesy of the John Carter Brown Library at Brown University.
Silver Mining and Refining in Colonial Peru
Early Peruvian Mining
Peru has a long history of silver mining and refining dating to over 2,000 years ago 1. The earliest Peruvians used silver, copper, gold, and other precious metals for jewelry, personal adornments, decoration, and religious ceremonies. Silver, copper, and gold have been found in necklaces, jewelry, and serving bowls of high-status people and were markers of power, privilege, and prestige. Precious metals have also been found in sunken courts and other ritual and religious locations 2. By the 15th and 16th centuries, the Inca Empire's kings and queens used gold and silver to decorated their religious temples and palaces, as well as for their own personal jewelry.
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Colonial Period Forced Labor
After the Spanish Conquest of the Inca Empire in 1532, the silver mining industry in Peru boomed. Spain used Peru's mineral wealth to fund the growth of their empire. However, mining had negative effects on the native people of Peru. Many were forced to labor in mines and camps 3. Potosí, located in present day Bolivia, was the location of the largest and richest silver mine in the Americas 4. The compulsory Potosí labor draft forced thousands of Peruvians and enslaved African miners to labor in silver mines and refineries 5. Working conditions were brutal, with exposure to dangerous and unstable tunnels and mining shafts. Refiners were exposed to poisonous dust mixed with mercury, sulfur, and arsenic from the refining process 6.
The Patio Process
By the end of the 16th century, most high-quality silver ore had been mined out of the region. The Spanish had to find new ways to extract silver from the lower-quality ore left behind. In AD 1554, a new technique called the patio process was developed, which used large amounts of mercury to extract silver from the low-quality ore 4. First developed in Mexico, the patio process arrived to Peru in AD 1571 and quick spread throughout the Spanish colonies 5. The patio process took place at water-powered silver refineries. Large batches of low-quality ore were ground with mills stones. The ground ore was then mixed with water, salt, copper sulfate, and mercury. The mixture was spread out in patios where it was left in the open sun to form an amalgam, or an alloy of bonded mercury and silver. The silver/mercury amalgam was then separated and heated, driving off the mercury. The remaining pure silver was shaped into ingots and bars for transport 5.
An aerial photograph of the archaeological site of Chorrillos, a 17th century Spanish silver refinery near Puno, Peru. The water canal used to sort silver ore is in the foreground of the photograph. Dark staining in the soil reflects areas of intensive grinding and heating of the silver ore. Photograph by Sarah Kennedy.
Left: Ink engraving from 1706, depicting mining operations at Cerro Rico, PotosÃ, in present-day Bolivia. This was the location of the richest silver mine in the Americas. In the engraving, men climb up and down a ladder carrying ore from the mine. Other men are depicted holding lights and using pickaxes to extract the ore from within the mine shaft.
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The text that accompanies this engraving describes how laborers worked 150 fathoms below the ground (275 meters, or 900 feet) and carried out the ore using a series of double-sided ladders made from ox hides and wooden poles. Courtesy of the John Carter Brown Library at Brown University.
Below: An ink engraving from 1789 depicting African slaves working in a Peruvian mine. Some individuals use pickaxes to extract ore. Another smelts the ore in a vessel, while another uses a bellows at a foundry. All are supervised by men in European dress. Courtesy of the John Carter Brown Library at Brown University.
