Crust minutely thick, rugulose, rimose, ashy-grey-white or white; apothecia minutely large, adnate, disc minutely plane (or with age slightly convex), pruina blue-white +/- dense, covered or uncovered, margin moderately thin, subpersistent; hypothecium nearly uncoloured; spores ovoid.

In Norway, circa Christian pl. loc. on schist clay v.c. Tidselholmen, Loenelv, Thorshough (N. G. Moe).  In Finland at Simonsby par. Pargas (F. Elfving).

It is similar to B. pruinosa at the same time each relatively better developed .—Apothecia 1-2 mm broad.  Excipulum entirely (exterior intensely) dark brown/grayish-brown-black; disc dark purple or dark carenous green when moistened.  Hypothecium colourless or slightly yellowish.  Hymenium 0.2-3 mm or a little taller.  Paraphyses slender, coherent, apices dark brownish/grayish-brownish; asci ventricose-clavate.  Spores 0.0040-45 mm long and 0.0025-40 mm thick, (in short) ovoid, but apparently often globose; in fact, when examined in water such a floater is arranged along a longitudinal axis.  Iodine wine-yellowish brownish (especially asci), preceding bluish fleeting or persistent, which varies in the same specimen.  NO₃ barely changes colour, except that the excipulum comes out more dark brown/grayish brown; K almost does nothing.—Crust K or CaCl not otherwise coloured; iodine hyphae not becoming bluish.