Description: Thallus crustose, episubstratic, rimose-areolate, white to yellowish white, but usually blue-grey pruinose, often delimited by a black prothallus. Areoles discrete, developing on a black prothallus, 0.4-0.6(-1) mm wide, each one with a single, well-defined, round and crater-like, laminal soralium bearing blackish, granular, 40-50 μm thick soredia. Medulla white, I+ blue. Apothecia extremely rare (not observed in Italian material). Photobiont chlorococcoid. Spot tests: medulla K+ yellow turning red (needle-like crystals), C-, KC-, P+ yellow-orange, N+ red. Chemistry: medulla with norstictic acid.
Note: on siliceous rocks in open lichen communities near or above treeline (i.e. near glaciers); probably more widespread in the Alps, but overlooked, being mostly sterile.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)