Description: Thallus crustose, episubstratic, rather thick, composed of densely packed, pulverulent granules, whitish to partially grey-brown or grey. Apothecia biatorine, black, 0.2-0.6 mm across, strongly constricted at base and sometimes substipitate, with a flat to to finally convex disc, and an up to 0.05 mm thick, finally excluded proper margin. Proper exciple thin, of radially arranged hyphae, dark olivaceous green and K+ green in outer part, colourless within; epithecium green to olive and K+ green, or purple-brown and K+ purple; hymenium colourless or pale purple, c. 50 μm high, I+ blue turning red; paraphyses coherent, thin, mostly simple; hypothecium dark purplish brown, K+ slowly purplish, N+ purple-red. Asci 8-spored, cylindrical-clavate, the I+ blue tholus with a wide, I+ dark blue tube structure. Ascospores 1-celled or 1-septate, oblong to subfusiform, rarely ellipsoid, 9-17(-21) x 2.5-5 μm. Pycnidia black, sessile, to 0.15 mm across. Conidia short-bacilliform, to 5.5 μm long. Photobiont micareoid, the cells 4-7 µm across. Spot tests: K-, C-, KC-, P-. UV-. Chemistry: thallus without lichen substances.
Note: on bryophytes and plant debris on the ground and amongst rocks, in areas with siliceous substrata, with optimum near treeline; probably more widespread in the Alps. The species is heterogeneous; according to Hafellner (2001) all material from at least the eastern Alps is morphologically different from H. crassipes s.str., and belongs instead into H. pulverulum.
Growth form: Crustose
Substrata: soil, terricolous mosses, and plant debris