Description: Thallus fruticose, erect, stiff, brownish black to black, shiny, simple or dichotomously branched, firmly attached by a basal holdfast, forming 3-5 cm wide, 1-3 cm tall tufts. Branches 0.3-0.7 mm wide, flattened in upper part, terete towards the base, without pseudocyphellae. Cortex 2-layered, with a thin, brownish, paraplectenchymatous outer layer and a very thick, colourless, prosoplectenchymatous inner layer; medulla white, dense. Apothecia usually common, lecanorine, terminal or subterminal, 2-5(-7) mm across, with a black disc with a a few cylindrical projections, and a concolorous thalline margin. Asci 8-spored, clavate, Lecanora-type. Ascospores 1-celled, hyaline, broadly ellipsoid, 5-6 x 3-4 µm. Pycnidia black, on the margin of branches. Conidia dumbbell-shaped (thickened at both ends), 6-8 x 0.5-0.8 µm. Photobiont chlorococcoid. Spot tests: cortex and medulla K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a circumpolar, arctic-alpine lichen found on hard, wind-exposed siliceous rocks, with optimum above treeline; common only in the Alps, but reaching the southern Apennines in Calabria and the mountains of Sicilia.