Gyalideopsis crenulata

Gyalideopsis crenulata is a species of saxicolous (rock-dwelling) lichen in the family Gomphillaceae. This inconspicuous lichen forms thin, pale grey to brownish films on rock fragments and is distinguished by its tiny, dark fruiting bodies with distinctively scalloped margins that give the species its name. It appears to be a specialist of disturbed mine spoil environments, where it grows on flat stones lying on fine material that provides the damp conditions it requires. It is known only from two copper-mining sites in Wales....read more on Wikipedia.