Description: Thallus crustose, episubstratic, rather thin, continuous to rimose-areolate, grey, dark grey to almost black, sometimes delimited by a dark prothallus. Areoles flat to slightly convex, often rounded, 0.3-1 mm wide, bearing punctiform to orbicular, 0.2-0.8 mm wide, flat, yellowish white to ochre, rarely finally grey, often abraded soralia with farinose soredia (50-80 μm diam.), which sometimes develop shiny black tips and resemble isidia. Apothecia rare, lecanorine-aspicilioid, immersed in the thallus, 0.3-0.6 mm across, with a black, epruinose disc and a thin thalline margin; proper margin well-developed. Epithecium olive-green, N+ emerald green; hymenium colourless; paraphyses sparingly branched, moniliform in upper part, the apical cell to c. 3 μm wide. Asci 8-spored, clavate, the thin outer coat K/I+ blue, the wall and apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid, 18-30 x 9-15 μm. Photobiont chlorococcoid. Spot tests: thallus K+ yellow turning red (needle-like crystals), more rarely K+ persistently yellow, C-, KC-, P+ bright to golden yellow. Chemistry: norstictic acid, more rarely stictic acid as a major substance.
Note: a chemically variable species (see Roux & coll. 2014, 2020), found on siliceous rocks, sometimes also on pebbles, certainly more widespread in the Alps, but very much overlooked.
United States National Herbarium - Smithsonian – CC BY-SA NC Austria, Stiria, Montes Koralpe, in confinibus Stireae Carinthiaeque loco Hebalm dicto. Leg. J. Poelt http://lichenportal.org/portal/taxa/index.php?taxon=124896