From the time that Columbus arrived in the Caribbean until Spain surrendered power over its mainland American colonies in the early 19th century, Spanish and Portuguese colonial mines poured forth vast amounts of bullion, including some gold and a far greater quantity of silver, both in terms of weight and its overall value relative to gold. Fiscal records indicate that Spanish Americans officially refined gold worth approximately 374,000,000 pesos, each consisting of 272 maravedís, whereas the amount of silver produced reached a value of 3,432,000,000 pesos (to these figures need to be added contraband output, estimated to have been around 17–20 percent). In other words, the colonies refined nine times more silver than gold. While Columbus, Cortés, and other earlier explorers may have fantasized primarily about gold, it was the flood of American silver that touched off the price revolution in Europe and monetarized the emerging world economy, especially because China had a voracious appetite for silver, not gold. At the same time in the American colonies, mining distorted economic life because of the incentives the industry received from a silver-hungry monarchy. Mining also had profound consequences for indigenous society, severely exploited to provide workers for the mines and refining mills.
Colonial refiners used two methods to beneficiate their silver ores, smelting and amalgamation. Smelting was suitable for all types of American silver ores but required large amounts of fuel to heat the ovens. It remained widely used throughout Mexico during the entire colonial period. Amalgamation was a newer technology, adapted to American ores during the mid-16th century. Although it did not require large quantities of charcoal and other fuels, as smelting did, amalgamation depended on the availability of mercury. Nearly all quicksilver used in colonial Spanish American silver mining came from either Huancavelica (Peru) or Almadén (Spain), with occasional supplements from Idria (Slovenia). Whereas both smelting and amalgamation were used widely in Mexico, Andean mines relied on amalgamation.
This article examines the long history of Potosí, Bolivia, home of the world’s most productive silver mines. The mines, discovered in 1545 and still active today, are discussed in terms of their geology, discovery, productivity, labor history, and technological development. The article also treats the social and environmental consequences of nearly five hundred years of continuous mining and refining.