Description: The grey, strongly cracked thallus of this crustose lichen will be seen on acid rocks near the coast. The discs (to 2mm diam.) are situated within islands of thallus (areoles) and are buff-coloured and glazed over, as if with ice. The discs may be blackened as they are occasionally the home of Arthonia varians, a parasitic lichen species. L. rupicola occurs on suitable habitat throughout Ireland, especially on well-lit siliceous rocks near the sea. A dab of fresh bleach turns the discs yellow.

Key Identification Features:

• The grey thallus and the beige to pink, pruinose, flattened apothecia indicate this species
• The discs give a yellow reaction with C, the thallus is K (Potassium hydroxide) + yellow.

Original text submitted by Simon Davey

Distribution Map from NBN: Glaucomaria rupicola var. rupicola at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Glaucomaria rupicola var. rupicola at iNaturalist World Species Observations database.