Black slate : surface alteration due to fungal activity Black slates of different oxidation states and graphite samples as pure carbon source were incubated with the white rot fungus Schizophyllum commune 4 39 for 3 months. Investigations by SEM showed fungal affinity to rough surfaces. Oxidatively weathered bleached black slate samples have more micropores and increased surface roughness than unweathered samples. Unpolished and polished bleached black slate samples were colonized best by fungal hyphae. The hyphae often entered pores. Etch pits induced by fungal activity could be observed which were then quantified by vertical scanning interferometry (VSI). The etch pits measured 3 4 m in width and 180 200 nm in depth. In contrast to black slate samples more etch pits were found on graphite surfaces. Moreover they showed a more elongated morphology and branches reminiscent of fungal growth morphology. Under laboratory conditions Schizophyllum commune was able to degrade about 0.03 m3 m2 rock material during 3 months of incubation. It could be shown that collapsed hyphae material remained in their etch pits even after sample preparation which was caused by strong fungal fixation to the rock surfaces. The higher carbon content and the softness of pressed graphite thus allow for earlier fungal attachment and higher dissolution rates. Amounts of nitrogen could be proved by chemical analyzing techniques (x ray photoelectron spectroscopy and electron microprobe) at all incubated rock samples. Nitrogen increased eminently on rock surfaces due to fungal colonization. Amounts of nitrogen were detected both on hyphae and former hyphae attachment areas. This indicates the presence of fungus and or fungal excreted proteins such as hydrophobins for attachment or enzymes for degradation.