Description: Thallus crustose, episubstratic, finely rimose-areolate, bluish grey to grey, sometimes partly rust-red when growing on iron-rich substrata, rarely poorly evident, often delimited by a black prothallus. Medulla white, I+ blue. Apothecia lecideine, arising between the areoles, black, 0.7-2 mm across, semi-immersed to almost sessile, usually crowded, with a slightly concave to slightly convex, epruinose, often fissured disc, and a raised, finally poorly evident proper margin. Proper exciple blue- to blackish-green in outer part, colourless or rarely pale brown within; epithecium brown-green to olive-green, N+ purple-red; hymenium colourless, 70-100 μm high; paraphyses simple or sparingly branched and anastomosing, coherent; hypothecium dark brown, 90-100 μm high. Asci 8-spored, narrowly clavate, thick-walled, with a K/I+ pale blue tholus and a strongly amyloid, thin apical cushion, surrounded by a I+ blue outer layer, Lecidea-type. Ascospores 1-celled, hyaline, ellipsoid to narrowly ellipsoid, (7-)9-12(-13.5) x 4-6 μm. Photobiont chlorococcoid. Spot tests: thallus and medulla K-, C-, KC-, P-, UV-. Chemistry: confluentic acid, 2’-0-methylperlatolic acid, rarely stictic acid.
Note: a boreal-montane to arctic-alpine, circumpolar species (Hertel 2006), found on low siliceous stones and boulders with a long snow-lie, with optimum near treeline; most common in the Alps, much rarer in the high Mediterranean mountains.