Thallus rimose, up to 10 cm diam.; hypothallus indistinct; areolae up to 0.5 (–1) mm diam., medium grey to pale ochraceous, dull, angular, plane; medulla KI–. – Apothecia up to 1.5 mm diam., black, epruinose, orbicular, weakly concave to weakly convex, with a thick and persistent margin and sometimes an umbonate disc; excipulum dark brown in the rim, inner part paler brown, K–; hypothecium reddish brown, K–; hymenium colourless; epihymenium olivaceous green to olivaceous brown, K–; no crystals or granules in the apothecia; ascospores 8 per ascus, eumuriform, persistently colourless or becoming faintly brown with age, 30–40 × 14–18 µm. – Conidiomata not seen.
No lichen substances.
On siliceous rock, mainly in the inundation and spray zones by streams and lakes.
The species resembles R. reductum, and some specimen may be difficult to identify. The description given above is based on typical specimens and may not cover the whole variation range of the species.