Type locality: Norway, Hordaland, Granvin, Skålsæte, på bergvegg av skifer (= on slaty rock wall), 1949, J. J. Havaas (lectotype UPS - selected here).

Description: Thallus crustose, "composed of orange-yellow to yellow-orange, scattered to contigous verruculose, 0.1- 1.0 mm in diam. and 0.15-0.4 mm thick areoles or squamules forming up to 2.5 cm large patches or growing along crevices of the substrate. Prothallus absent or present and then pale, very thin, up to 0.5 mm wide at margin of thallus. Apothecia abundant, sessile to raised, round to irregular, zeorine, 0.4-1.2 mm wide; disc ± plane, sometimes flexuose, orange; proper margin 40-75 μm thick, slightly paler than and raised above disc; thalline margin mostly present, 25–75 μm thick, even to somewhat crenulate, concolorous with thallus; hymenium c. 75 μm thick, hyaline, hypothecium 65-70 μm thick, hyaline; paraphyses simple, 2-2.5 μm wide with upper cells slightly wider, up to 4(-5) μm; Ascospores polaribilocular, ellipsoid, 12.5-17.0 x 5.0-6.7 μm, septum 3.7-6.5 μm, ratio spore length/septum 2.50, ratio septum/spore length 0.34. Pycnidia unknown" (Arup 2006: 35-36).

Photobiont: Data lacking.

Chemistry: "Parietin occurs as a major compound, together with small amounts of fallacinal, emodin, teloschistin and parietinic acid, which corresponds to chemosyndrome A of Søchting (1997)" (Arup 2006: 35-36).

Ecology: At the type locality C. havaasii grows on horizontal to vertical surfaces under overhangs of calciferous slate. This locality is located on a mountain at c. 560 m altitude.