(crustose)? lichen

(crustose)? lichen

Observation - (crustose)? lichen - UK and Ireland. Description: greenish grey (crustose) lichen growing on sandstone paving slab. I'm not sure if this is crustose or very small foliose.

greenish grey (crustose) lichen growing on sandstone paving slab. I'm not sure if this is crustose or very small foliose.