Thallus crustose, white to sordid or dull drab grey, forming a thin, almost evanescent to moderately thick, uneven, rimose-cracked, continuous crust, occasionally occurring as dispersed, roughened, convex granules. Prothallus indistinct. A pale aeruginose-blue coloration (copper oxalate) is frequently visible in cracks and abraded areas. Anamorph: conidiomata pycnidia, ca 500 µm diam., conspicuous especially where the thallus is poorly developed, usually numerous, crateriform with a + elevated, conspicuous thalline margin. Conidia 10-15 x 0.8 µm, narrowly bacillar, straight, hyaline. Teleomorph: ascomata apothecia, 1-3 mm diam., sessile, matt black, occasionally ± pruinose, usually at first flattened with a narrow even margin, becoming irregularly convex or sublobate and emarginate, occasionally remaining flattened, with a thin, persistent, markedly flexuose margin. Exciple often poorly developed and soon excluded, the edge olive brown, gradually becoming colourless within and towards the hypothecium. Hypothecium with an upper pale brown part ca 15 µm thick, the hyphae vertically orientated, the lower part becoming dark brown-black and 110-230 µm thick, with unorientated hyphae. Hymenium 45-55 µm high, hyaline. Epithecium well defined, drab brown-olive, K+ dull greenish, N+ purple-red. Interascal tissue of unbranched paraphyses ca 2 µm diam. with slightly swollen brownish apices (to 2.5-3 µm diam.), conglutinate, not separating in K. Asci clavate, 22-45 x 6-9 µm, 8-spored. Spores 8-11 (-13) x (2-5)-3 (-4.0) µm, cylindric-ellipsoidal, hyaline, aseptate. Chemistry: Thallus C–, K–, KC–, Pd–, UV+ white (perlatolic acid in the thallus; an unidentified substance, probably anziaic acid or a derivative, in the exciple). Medulla usually markedly I+ blue or violet.