Since the 1990s, conflicts over mining activity played a prominent role in Peruvian politics and have put the environment at the forefront of the public agenda. While Peru has a long history of mining, the country’s role as a key mineral exporter is not simply a consequence of the amount of mineral wealth within its territory. Shifts in global investment flows, neoliberal reforms, and innovations in mining technologies have expanded the frontiers of extraction into areas formerly used for agriculture and farming. A review of literatures in science studies, political ecology, and the anthropology of mining introduces theoretical tools that will be used to examine how mining expansion brought water, toxic chemicals, agentive mountains, and other actors into the sphere of politics. The concept of equivalence serves to explore how scientific and nonscientific forms of knowledge make pollution perceptible (or imperceptible), politically significant, and the focus of controversy.