Description: Thallus crustose to subleprose, whitish, whitish grey to grey, entirely consisting in a mass of granules, usually well-delimited, sometimes indistinctly sublobate at margin. The thallus starts developing as isolated, dispersed granules that form piles, or aggregations (best visible along the margins, where the dispersion of the young granules is most readily observed) which eventually overlap and become confluent, giving the false appearance of a continuous thallus in older areas. Granules rather firmly attached, coarse, up to 200(-300) μm in diam., with a compact, pseudocorticate surface, without projecting hyphae. Medulla absent or very thin. Hypothalline hyphae usually scarce, whitish grey, grey to blackish grey, rarely pale yellowish orange-brown, in which case they react K+ purple-red. Photobiont chlorococcoid. Spot tests K+ yellowish, C-, KC-, P- or P+ faintly yellow, UV+ orange-brown; hypothalline hyphae sometimes K+ purple-red. Chemistry: atranorin, plus 2 unidentified fatty acids; sometimes anthraquinones in the hypothalline hyphae.
Note: overgrowing mosses, mostly on siliceous boulders, rarely in shaded fissures of the rocks; not common at high elevations in the European orobiomes but perhaps also overlooked or confused with similar species, with a few records from the Eastern Alps (Austria). To be looked for in the Italian Alps.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)