Distribution: N - Frl (Tretiach & Hafellner 2000), Ven (Hertel & Schuhwerk 2010), TAA (Lang 2009, Hertel & Schuhwerk 2010, Watson 2014), Lomb (Brackel 2010), Piem (Morisi & Sereno 1995, Isocrono & al. 2004, 2006, Isocrono & Piervittori 2008), VA (Piervittori & Isocrono 1999, Piervittori & al. 2001, Isocrono & al. 2008, Matteucci & al. 2015c), Emil (Dalle Vedove & al. 2002, Tretiach & al. 2008, Fariselli & al. 2020), Lig (Brunialti & al. 1999). C - Tosc (Tretiach & al. 2008), Sar (Nöske 2000, Brackel & Berger 2019). S - Camp, Bas, Cal (Puntillo 1996), Si (Brackel 2008b, 2008c).
Description: Thallus crustose, episubstratic, usually < 1 mm thick, rimose to usually areolate, chalky white to whitish grey or sometimes rust-red or ochre (due to incrustations of iron-oxides), often delimited by a black prothallus. Areoles relatively small (<1 mm across), angular, contiguous, flat to slightly convex. Cortex without an epinecral layer; 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, 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; epithecium greenish black to brownish black, 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 almost colourless to pale 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, 9-16 x 4.5-8 µm. Pycnidia black, immersed. Conidia bacilliform, more or less straight. Photobiont chlorococcoid. Spot tests: thallus K+ yellow turning red (needle-like crystals), C-, KC-, P+ yellow-orange. Chemistry: norstictic acid syndrome.
Note: doubtfully distinct from var. lapicida and perhaps just a chemical strain of the latter, with a similar distribution and ecology, this taxon is widespread and common in upland areas throughout the country, but most frequent in the Alps. The record from Venezia Giulia in Nimis (1993: 384) has been excluded, as it actually is from Slovenia.