Lepraria incana (L.) Ach. forme saxicole des parois verticales.
Crustose thallus that can occupy large areas over several m², thick to very thick, strongly cracked by deep crevices which delimit slightly domed areoles which draw like a paving, surface powdered by fine elongated granules in the manner of globular isidia, midnight blue, pale blue, greyish-blue, greenish-grey, purplish-grey, celadon-green, etc., often stained with rust-brown or purplish-brown in old or necrotic areas and also often covered by algae (Trentepohlia). Not fertile. C-, K-, KC-, P- but these reactions are difficult to observe because the surface of the thallus is hydrophobic. Typically growing under siliceous rocks or in the vertical walls of slate quarry excavations in places sheltered from light and direct rain, often in company with Scoliciosporum umbrinum in shady places and Psilolechia lucida in places receiving more light.