Thallus to 20 cm diam., rather thick, becoming wide-spreading, rimose at the edge to warted-areolate. Areoles 0.3-1(-2) mm diam., continuous, flat or convex, occasionally subsquamulose in the centre of the thallus, irregular to rounded, often uneven with distinct edges and a rough, matt surface, typically pale grey with a blue tinge, becoming dirty dark grey. Prothallus, if present, grey, delimiting. Anamorph: conidiomata pycnidial, conidia 6-12 × ca 1 μm. Teleomorph: ascomata apothecia, 0.2-0.8 mm diam., immersed, crater-like, sometimes becoming emergent, well separated. Thalline margin evident from an early stage, thin, entire, somewhat wavy, but rarely prominent. Disc black, shiny, concave, becoming expanded. Asci cylindric-clavate, thin outer coat K/I+ blue, wall and apical dome K/I–, (4-)6-8-spored. Ascospores very variable in size, often poorly developed, 14-30 × 7-16 μm, broadly ellipsoidal, aseptate, hyaline, thin- and smooth-walled, without a gelatinous sheath or epispore. Chemistry: cortex and medulla K–, Pd– (aspicilin).