The silver produced by indigenous mine workers in Potosí, Bolivia, helped fuel early modern global trade. While historiography has analyzed the structure of the labor force, one important question has not been addressed: how workers themselves acted on and changed the conditions imposed on their lives. This article argues that they fundamentally shaped Potosí's labor system. I analyze, then, the interaction between coerced and free labor—mitayos and mingas—and emphasize their interconnection with k'ajchas (self-employed workers) and the rudimentary ore mills known as trapiches. The article demonstrates how k'ajchas and trapiches contested the property rights of the traditional Spanish mine- and millowners in Potosí. I also highlight the key role of women in refining and trading ores, which challenges standard gender assumptions about mining labor. By the eighteenth century a heterogeneous popular economy broke the monopoly over production once held by Spanish mine- and millowners.