Critical minerals and metals are essential to energy, electronics, transportation, and national security, yet many conventional resources face growing supply pressure. Unconventional Earth materials and waste streams, including mine tailings, red mud, coal-related residuals, acid mine drainage treatment solids, sedimentary deposits, and other mineral-dominated systems, represent important but still poorly understood potential sources. This session invites contributions that examine the biogeochemical processes controlling the occurrence, distribution, speciation, mobility, and recovery of critical minerals and metals in unconventional systems. Relevant topics include microbe-mineral interactions, redox transformations, biomolecule and ligand-mediated processes, nanoscale host phases, weathering and transport, metal sequestration and release, biomining and bioleaching, and multiscale characterization of critical mineral behavior in natural and engineered environments.