Mining development often threatens rural areas with dispossession, but these processes foment learning and opposition by locals, their grassroots organisations, and transnational solidarity campaigns/movements. Emergent solidarity nexuses are sites of knowledge production and amplify grassroots struggles. This article explores how a local grassroots struggle against a proposed mining project at Ro?ia Montana, Romania was catalysed by processes of incidental learning--through local experiences with preparatory development--which gave rise to more intentional forms of local learning and place-based praxis. The formation of a growing trans/national solidarity network arose from these early efforts and intertwined with the grassroots struggle, augmenting knowledge production with non-formal and formal approaches to learning. Knowledge was produced through various forms and towards critical, informational, tactical, and strategic purposes. The findings herein contribute to the literature on a broadened understanding of adult education from the lens of learning in social action. Further, this article offers an exploratory description of the processes of learning in social action at a nexus of grassroots struggle and a trans/national solidarity network and contributes to an understanding of how diverse forms of learning in social action are integral to processes of local and national social change.