A crustose species easily recognisable by the dense covering of dark blue-grey, granular soredia. A blue-black prothallus is usually present.
Thallus and soredia: C-, K+ yellow, UV-
In Scotland, Tephromela grumosa has a mainly south-eastern distribution where it is found on well-lit siliceous rock, including gravestones. BLS distribution map
scottishlichens.co.uk 