The energy transition has increased the demand for critical minerals, in particular lithium, generating new governance challenges and heightening tensions across various territories. In this context, resource management policies and tools are gaining growing significance. The United Nations Framework Classification for Resources (UNFC) has become particularly relevant as a tool for guiding the sustainable management of resources. Commonly viewed as a technical classification framework, this thesis examines how UNFC—especially its E-axis—can also function as a public policy instrument with structuring, governing, and performative effects. Using the Jadar lithium project in Serbia as a case study, this research explores how classification can shape perceptions of project viability, embed values, assign responsibility, legitimize certain narratives, and structure decision-making. This thesis ultimately argues that UNFC operates not only as a technical framework, but also as a governance instrument that shapes the field of action.