Description: Thallus crustose-placodioid, episubstratic, rather thin, forming up to 3(-4) cm wide, more or less orbicular rosettes, rimose-areolate, greyish white to bluish grey, delimited by a dark prothallus. Apothecia lecanorine-aspicilioid, more or less circular, 0.2-0.5 mm across, immersed in the thallus, with a black, epruinose, flat disc, and a thin, poorly evident thalline margin level with thallus. Epithecium brownish green, N+ emerald green; hymenium colourless; paraphyses submoniliform; hypothécium colourless, I+ blue. Asci 8-spored, clavate, the thin outer coat K/I+ blue, the wall and apical dome K/I-. Ascospores 1-celled, hyaline, broadly ellipsoid, 13-25 x 9-18 µm. Photobiont chlorococcoid. Spot tests: thallus K-, C- , KC-, P-; margin of apothecia K-. Chemistry: without lichen substances.
Note: a species with a bluish-grey effigurate thallus, whose differences from A. candida are still in need of evaluation; the type, from South Tyrol, was on serpentine, but the species was also reported from slightly calcareous schists. It might have been confused with A. verruculosa.