Thallus crustose, dark grey (often purple tinged) or pale to dark brown, cracked areolate, areoles plane to verrucose. Soralia c. 01–05 mmdiam., initially discrete but becoming confluent, soredia initially concolorous with, or darker than the thallus, coralloid-granular, becoming pale yellow-brown, farinose. Photobiont chlorococcoid, cells thick-walled, 7–16(–19) 8–12(–13) mm, often dividing to give 2–4 daughter cells (Chlorella-type).
Anamorph: conidiomata pycnidia, frequent, 200-300 µm diam, dark brown to black, immersed in the thallus. Conidia 6–8 x 0.8 µm, bacilliform.
Teleomorph: ascomata apothecia, very rare, mature apothecia known only from the type collection. Identical to those of R. lugubris forma lugubris.