Description: This Caloplaca is one of the grey thallus tribe with black discs. Its appearance is more that of an Aspicilia. The thallus can be large or very small and has a zoned margin limited by a black line. The small black discs that are immersed at first can be hazy blue-grey frosted. The spore septum is about one-third the length of the spore. It grows on hard limestones. C. variabilis has a thinner, darker grey thallus with black sessile discs. In Ireland, there is a good range of records from the north-east and south-west.

Key Identification Features:

• Thick, pale grey thallus, discs black, immersed at first, very like an Aspicilia
• Hard limestones and boulders.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Pyrenodesmia chalybaea at iNaturalist World Species Observations database.