Distribution: N - VG (Castello 2002, Martellos & Castello 2004), Frl (Tretiach & Hafellner 2000), Ven (Hertel & Schuhwerk 2010), TAA (Nascimbene 2003, Lang 2009, Hertel & Schuhwerk 2010, Watson 2014), Lomb, Piem (Isocrono & al. 2003, 2004, 2006, Isocrono & Piervittori 2008, Giordani & al. 2014), VA (Borlandelli & al. 1996, Piervittori & Isocrono 1997, 1999, Piervittori & al. 2001, Isocrono & al. 2008, Favero-Longo & Piervittori 2009, Matteucci & al. 2015c), Emil (Tretiach & al. 2008, Fariselli & al. 2020), Lig. C - Tosc, Marc (Herb. Ravera 2777), Abr (Recchia & Villa 1996), Sar. S - Cal (Puntillo 1996), Si.
Description: Thallus crustose, episubstratic, rimose to usually areolate, white to bluish grey or sometimes rust-red or ochre (due to incrustations of iron-oxides), often delimited by a black prothallus. Medulla white, I+ intensely blue-violet. Apothecia lecideine, black, arising between the areoles, constricted at base, round or more frequently angular, 0.5-1.2(-2) mm across, with a flat to slightly convex, dull, smooth, usually epruinose disc, and a persistent proper margin. Proper exciple black-brown in outer part, colourless within, the unpigmented part 30-80(-120) µm wide, the pigmented part K+ and P+ yellow or K-, P-; epithecium greenish black to brownish black, uniformly thick, K+ bright blue-green; hymenium colourless, 45-80 µm high, I+ blue; paraphyses usually unbranched and rarely anastomosing, the apical cells, swollen, 3.5-5 µm wide; hypothecium pale to medium brown. 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, broadly ellipsoid, 9-15 x 5-8.5 µm, 1.5-2.9 times as long as wide. Pycnidia black, immersed. Conidia bacilliform, more or less straight, 11-22 x 1-1.3 µm. Photobiont chlorococcoid. Spot tests: K- or K+ yellow, C-, KC-, P- or P+ pale yellow. Chemistry: stictic acid syndrome.
Note: a circumpolar, arctic-alpine to boreal-montane and cool-temperate species (Hertel 2006) with a broad ecological range, found on hard, acid siliceous rocks, mostly in exposed, windy situations in upland areas, up to the nival belt in the Alps.