A very fine 'fungus'-eisenkiesel specimen with phantoms. Very glossy, clear quartz crystals including limonitized fossil bacteria, sitting on massive, fossil bacteria-induced stromatolites, replaced by limonite-quartz. You can clearly see the inclusions of archaea bacteria. Previously this material was thought to be fossil fungi mycelia, but newer scientific publications contradict this and suggest bacteria colonies responsible for the fibrous limonite structures. However, I think in some of the specimen certain 'knots' are apparent, which I'd define as mycelia spore containers. 
Excerpt from a scientific publication: "Fossil fungi in iron stromatolites from Warstein (Rhenish Massif, Northwestern Germany) Zeitschrift Facies Verlag Springer Berlin / Heidelberg ISSN 0172-9179 (Print) 1612-4820 (Online) Heft Volume 7, Number 1 / Dezember 1982 DOI 10.1007/BF02537228 Seiten 237-259 Fossil iron stromatolites, formed by fungi, have been found near Warstein, W. Germany. The stromatolitic and massive ferruginous quartzes are always confined to karstic hollow molds of the Devonian "Massenkalk". The few occurrences show that these are chalcedony-quartz-silicifations of mainly ac-oriented, corrosively widened cracks. A mineralization temperature of about 120°C was found by microthermometrical measurements. Druses in ferruginous quartz sometimes carry clear, prismatic to pseudocubic quartzes embedding fungal mycelia. The fungal filaments are generally encrusted with goethite and appear in stromatolitic, massive and patch-like forms. An Oligocene/Miocene age is presumed ... "Anyway this is a worldwide singular geological phenomenon in the Sauerland area.