From the late 16th century to early 18th, silver mining was the economic engine of empire in the Andes, playing a significant role in Spain’s European ambitions and the forging of global trade. Yet this productivity came at a terrible cost for Andean people forced to work in the mines, and colonial critics forcefully debated the morality and legality of the mining economy even as it became essential to the colonial project itself. More than any others, the mercury mines of Huancavelica, Peru became synonymous with this conflict between the human toll of colonial exploitation and immense mineral wealth of the Andes. As the only Andean source of the mercury required to refine silver and a mine infamous for its toxic conditions, Huancavelica became a crucial source of debate over the conditions in which the Spanish Empire could and should employ forced labor. Royal officials attempted to soothe pious critics, maintain mercury production, and preserve the Andean labor force while Spanish miners and Andean communities vied for their own interests. This article examines conflicts over nocturnal labor to shed light on these dynamics, challenging simplistic understandings of labor relations at the mines where Andeans actively advocated for themselves, miners challenged royal policy, and even seemingly favorable conditions failed to yield tangible reforms.