Description: Thallus crustose, episubstratic, forming small, 1-2 cm wide rosettes, areolate, pale to dark grey or brownish grey, sometimes delimited by a black prothallus, but most often distinctly lobed and almost placodioid, the central parts with 0.2-0.4 mm thick, isidia-like, cylindrical, simple or sparingly branched papillae which sometimes give rise to apical soralia. Medulla white, I-. Apothecia very rare, up to 1 mm across, immersed to slightly protruding, aspicilioid, with a black disc and a thin, poorly evident, sometimes sorediate thalline margin. Asci 8-spored, clavate, the thin outer coat K/I+ blue, the wall and apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid, 12-27 x 8-15 µm. Pycnidia black, immersed. Conidia 12.5-19 µm long. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-; medulla K+ intensively yellow. Chemistry: substictic acid in the medulla.
Note: on basic siliceous rocks, often on weakly calciferous schists, in humid-shaded situations near and above treeline, up to the nival belt; to be looked further throughout the Alps. For further information see Tretiach & Hafellner (2000).