Mineral extraction sites have been shown to serve as secondary habitats and provide suitable conditions for a wide range of plant species. The areas created by extraction are characterized by a high degree of disturbance, nutrient depletion, and low competition. Here, we compare plant communities across a wide range of sites and substrate classes, to assess drivers of plant biodiversity and provide practical insights for restoration that can be applied by extraction companies. We studied alpha- and beta-diversity of plant species in 12 German mineral extraction sites for building materials (gravel, gypsum, limestone, sand). We assessed plant diversity, abundance, and abiotic and structural parameters on 124 plots. We found only minor variation in species richness between plots, whereas species composition differed substantially. Species richness increased with soil pH while it decreased with proportion of open soil. The local contribution to beta diversity (LCBD) of sites was particularly high on open and acidic plots. The acidic and older plots harboured the highest proportion of endangered species. The floristic composition was significantly influenced by age, herb-layer height, open soil, and pH; however, site and substrate accounted for a substantially greater proportion of the total variance in community composition. Our findings highlight the significance of open pioneer habitats in driving plant beta diversity of extraction sites for building materials. Nutrient depletion and site heterogeneity facilitate the colonization by a wide range of generalist and specialized plant species through natural succession. Given the excellent nutrient-poor starting conditions, mineral extraction sites should therefore be prioritized for the development and restoration of low-productive open habitats, such as grass- and heathlands, while common recultivation measures, in particular soil amelioration and afforestation, should be avoided. The persistence of open pioneer habitats can be promoted by deliberate mechanical disturbances or grazing to slow down succession on abandoned patches. Addressing shortcomings in long-term management and advancing the development of post-extraction habitats for conservation purposes is crucial and could make a substantial contribution to the protection of plant diversity at both local and regional scales.