[2] Porpidia species primarily inhabit siliceous rocks, pebbles, and stonework, with rare occurrences on bark, wood, and compacted soil.

The thallus can vary in appearance, from thick and scaly to almost invisible, and may be solid or cracked into small pieces called areoles.

The lichen's inner structure, or medulla, may or may not react with iodine (I+ or I–), and some species produce powdery soredia for reproduction, while others do not.

These round, dark brown to black discs are often relatively large, ranging from 0.5 to 3 mm in diameter, and may be coated with a frosty layer (a pruina).

The rim surrounding the apothecia is usually dark blue-black or brown, and made of tightly packed fungal filaments.