Description: This little crustose lichen is a commonly occurring species of siliceous rocks and walls. Brick-built garden walls in urban areas are especially favoured. The small, black discs (to 0.5mm) with a distinct rim, sit on a greenish-grey thallus. It is widespread in Ireland.

Key Identification Features:

• The habitat, tiny black discs with a conspicuous rim and colour of the thallus help to distinguish the species
• Under the microscope the spores with a single division (one-septate) help to place it within Catillaria.

Original text submitted by Simon Davey

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

iNaturalist: Catillaria chalybeia at iNaturalist World Species Observations database.