Description: Thallus crustose, thin, endosubstratic and poorly evident or rarely thinly episubstratic and granular-verrucose, dark grey green. Apothecia stalked, pin-like, black with a thin whitish pruina which is most abundant at the edge and on the lower side of capitulum, or more rarely epruinose. Stalk shiny black, sometimes white-pruinose in the uppermost part, 0.5-0.9 mm high, of strongly sclerotized, dark brown to dark aeruginose, irregularly interwoven hyphae, the outer layer covered with a thin, transparent gelatinous sheath. Capitulum lenticular to obovoid, with a well-developed, cup-shaped exciple; mazaedium well developed, black; hypothecium dark. Asci cylindrical, formed singly, dissolving early, with uniseriate ascospores. Ascospores 1-septate, dark brown, ellipsoid, 9-13 x 5-7 µm, with a thick, ornamented wall; young spores with mainly longitudinally arranged ridges, mature spores with irregular cracks and short ridge fragments. Photobiont chlorococcoid. Spot tests: thallus K- or K+ dull yellow, C-, KC-, P-; ascomata I- in all parts. Chemistry: thallus with sekikaic acid (major) and related compounds.
Note: a temperate to boreal-montane, holarctic species found on lignum and on acid bark, especially on decorticated stumps of conifers, but also on broad-leaved trees, e.g. on Castanea, certainly widespread throughout the Alps (see note on C. abietinum).