In praise of geomycology Interactions between the microbially dominated biosphere and the geosphere have and are profoundly affecting our planet and all life on it. Geomicrobiology can be defined as the study of the role that microbes have played and are playing in processes of fundamental importance to geology, and within the diffuse boundaries enclosed by this definition, fungi are important components. Some of the major geological processes affected by microbial activities include mineral formation, mineral degradation (including weathering, bioleaching, soil and sediment formation), element cycling and fossil fuel genesis and degradation. The cycling of component elements from organic and inorganic substrates as a result of these processes can be termed biogeochemical cycling, which again emphasizes the interplay between physicochemical and biological mechanisms. The study of the roles and importance of fungi as agents of geological change can be termed geomycology and fungi are ideally suited for this purpose. The branching, filamentous mode of growth allows efficient colonization and exploration of solid substrates while extracellular release of enzymes and other metabolites mediates many organic and inorganic transformations. Considerable physical force can arise from hyphal penetration while translocation of resources through the mycelium enables exploitation of environments where nutrients have an irregular distribution. Fungi can attack silicates, carbonates, phosphates and other minerals while their carbonaceous predilections are well-known, extending to recalcitrant organic molecules of natural origin, e.g. lignin and chitin, or from anthropogenic activity, e.g. pesticides and other xenobiotics.