Description: This grey-white, powder-cottony, crustose lichen should be looked for on dry, siliceous or slightly calcareous rocks and walls where it can spread to form big-sized patches. The edge of the thallus is ringed by a conspicuous white-fringed border. Discs are small and red and are scattered like little spots of blood. A dab of K (Potassium hydroxide) will turn the thallus yellow. Pd turns it yellow.

Key Identification Features:

• White, circular patches with a powdery or cottony thallus surrounded by a chalk-white fringe — like rug edging
• On vertical sandstone walls and gravestones.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Haematomma ochroleucum var. porphyrium at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Haematomma ochroleucum var. porphyrium at iNaturalist World Species Observations database.