Description: This is a lichen of granitic rocks, monuments, headstones and chippings. The thallus is barely visible: a thin grey-green smear, but what are of note are the crumpled discs which squeeze in between crevices and cracks. Each disc is small (0.2-1.0mm diam.), rock hard and charcoal black with a thick, crumpled margin and a central umbo (a short stalk) protruding from its centre. It also grows on slaty rocks and along sea cliffs. North, south and south-east Ireland.

Key Identification Features:

• A compact mass of black, crumpled discs which creep into cracks and fissures of granitic rocks like a ‘death assemblage’ of little black mites
• The rounded discs are brittle and the exciple, crenulated like a cog wheel; each disc together with its umbo resembles the upturned cap of a black and wizened button mushroom.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Acarospora privigna at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Acarospora privigna at iNaturalist World Species Observations database.