Description: Thallus crustose-subsquamulose, 3-5 mm thick, forming 2-4(-5) cm wide, orbicular or irregular patches often delimited by a pale prothallus. Areoles constricted at base, convex-bullate, becoming subcerebriform, scattered to contiguous, 1-3 mm wide and 2-3 mm high, pale grey to pale brown, sorediate. Soredia finely granular, arising at the margins and lower surfaces of the areoles, pale yellowish green to pale brownish white (fading to white in the herbarium), arranged in initially concave, then convex, elongated to circular soralia which later become confluent and cover large parts of the upper surface, simulating capitate soralia. Upper pseudocortex overlain by an epinecral layer, pale brown, 20-30 μm thick, inspersed with small, pale yellow crystals partly soluble in K; medulla loose, white, the cells incrusted with coarse crystals insoluble in K. Apothecia rare, lecanorine to finally almost biatorine, broadly sessile, 1-1.5 mm across, with a greyish violet, brownish or bluish black, soon convex, usually somewhat pruinose disc, and a thin, irregularly sinuous, at first slightly raised proper margin; a bluish black parathecial ring is often also present. Thalline exciple with a strongly gelatinized cortex, the medulla with a few algae, loose, with anticlinally arranged, thick-walled hyphae; proper exciple colourless; epithecium olive green or dirty violet-brown, K+ green, N+ red, with greenish blue streaks penetrating into the hymenium; hymenium colourless, inspersed with oil droplets, 50-70 µm high; paraphyses strongly coherent, mostly simple, 1.5-2 μm thick at mid-level, the apical cells not or only slightly wider; hypothecium colourless. Asci 8-spored, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type. Ascospores 1-celled, hyaline, subglobose to ellipsoid, (6.5-)9-10(-13) x 5-7 µm. Pycnidia rare. Conidia filiform, often curved, 15-20 µm long. Photobiont chlorococcoid. Spot tests: cortex K+ yellow, C-, KC+ red, P-; soralia C+ pink to red, KC+ red, P+ yellow. Chemistry: atranorin, alectorialic acid, thamnolic acid, unknown substances.
Note: a recently-described species found on acid siliceous rocks near or above treeline; perhaps more widespread, but not common, in the Alps, where it reaches the nival belt.