Epilithic thallus usually lacking, rarely a finely areolate, 0.2 mm thick, sooty white to yellowish thallus developed. Apothecia usually small, less than 1 mm broad, with very narrowed base (sometimes imbedded in substratum when in calcareous rock), shining black, epruinose, flat or moderately swollen disk; margin persistent; exciple exterior black-green, interior hyaline to greenish or gray-opaque; hypothecium hyaline; epihymenium bright blue-green or very green to rarely olive-green; hymenium 70-110 μm, opaque with inspersed oil drops; paraphyses mainly simple, tips thickened to 3-5 μm; asci clavate; spores ellipsoid to broadly ellipsoid, thick-walled, 12-17 x 6.5-10 μm.

Reactions: K—, C—, P—, I—; hymenium 1+ blue with ascal tholus.

This species grows on both calcareous and silicate rocks. It appears to be circumpolar arctic-alpine and also occurs in Venezuela. The apparently disjunct specimen from Wisconsin has been checked by H. Hertel. A report by Magnusson (1945) from Greenland did not cite a specific locality. In North America it ranges south to Arizona.