Calicium abietinum, commonly known as fir pin or black stubble,[1] is a crustose lichen that is found growing on trees throughout much of the world.

The stalk is dark brown in longitudinal section, consisting of densely intertwined, sclerotized hyphae.

The outermost part of the stalk is +hyaline, with pale hyphae and a thin sheet of gelatinous material at the surface, often with a brownish or olivaceous tinge, or shiny black, and 0.08-0.13 mm wide.

[2] Spot tests show the thallus is K-, C-, KC-, P-, and the apothecia are I-.

[2] Calicium abietinum grows on wood, especially conifers and oaks, as well as on decaying stumps and logs, in the fringe areas of forests in moderate to rather strong light.