Thallus pale grey, initially squamulose but then, in its typical form, with tufts of ascending to erect, pale pinkish-orange branches (pseudopodetia), to 4cm, bearing abundant, rounded, flattened, deeply crenate scales (phyllocladia) that are grey in the centre when mature and damp, very variable in form but frequently reminiscent of smoke plumes from a volcano (hence 'vesuvianum'), globose clusters of soredia often present at the tips of the pseudopodetia, wrinkled brown to black cephalodia sometimes also produced; apothecia frequent, dark brown, button-like, on tips of upper side-branches. 

On siliceous and metalliferous rocks and stonework, occasionally on tops of urban walls.

All year round.

Fairly frequent but somewhat local in distribution. Often abundant in upland areas.

Rare and appears to be in decline. Currently known from only two sites.