Thallus areolate, up to 5 cm diam.; hypothallus indistinct; areolae up to 1.5 (–2) mm diam., pale grey or slightly brownish grey, dull, contiguous, angular, plane to weakly convex, smooth, thick; medulla KI–. – Apothecia up to 1.5 mm diam., black, often with a white pruinose disc, mainly orbicular, plane to weakly convex, with a persistent and usually epruinose margin; excipulum brownish black in the rim, inner part paler brown, lacking crystals, K+ red; hypothecium dark brown, K–; hymenium colourless; epihymenium dark brown, frequently containing crystals not dissolving in K, K+ red; ascospores 8 per ascus, submuriform, persistently colourless or becoming faintly brown with age, 20–40 × 12–22 µm. – Conidiomata not seen.
No lichen substances.
On rock in the mountains. Rarely collected.
The pruinose apothecial disc is diagnostic, but the character is not always developed.