Thallus crustose, rimose to areolate, white, rarely pale grey, to 5 cm wide, 0.3–0.5 mm thick. Areolae angular to irregular, 0.5–1.5 mm wide, plane and smooth to weakly convex, lacking isidia and soredia. Prothallus black, prominent between the areolae and at the thallus margin, or not apparent. Apothecia common, scattered to crowded, sessile, ±constricted at the base, 0.8–2.0 mm wide; disc ±plane, undulate or convex, ±round, glossy black, epruinose; thalline exciple usually prominent, thin, persistent, smooth, rarely reduced or not developed; proper exciple colourless, 100–200 µm thick. Epihymenium dark violet-brown. Hymenium violet to violet-brown, 50–60 µm thick, not inspersed. Hypothecium brown to yellow-brown, 100–150 µm thick. Ascospores simple, ellipsoidal, thick-walled, 9–11 × 5.5–7.0 µm. Conidia filiform, straight, 12–24 × 1.0–1.5 µm.

CHEMISTRY: Cortex K+ yellow, C–, KC–, P– or P+ pale yellow; medulla K–, C–, KC+ pink, P–, UV+ blue-white; containing α-collatolic acid (major), atranorin (minor), 4-O-methylphysodic acid (minor or trace), alectoronic acid (minor or trace), ±physodic acid (trace), ±bourgeanic acid (minor).