Lepraria caesioalba

A leprose species that forms grey, granular rosettes that tend to be darker in the centre. 

Thallus: C-, K+ faint yellow, UV.

In Scotland, Lepraria caesioalba is found in upland areas where it grows on well-lit or lightly shaded, exposed, siliceous rocks. BLS distribution map

Lepraria caesioalba at Caisteal Grugaig (Forestry and Land Scotland) overlooking Loch Alsh (VC105)