Umbilicaria phaea is a brown, umbilicate foliose lichen that grows up to 6 cm (2.4 in) in diameter, sometimes in colonies covering large patches of desert rocks.

[1] It is (monophyllous) with a single 1 – 5 cm flattish leaf-like cap on top of an anchoring stem (umbilicate).

[2] The leaflike top is smooth with some lobes, roughly circular, thin, and brittle.

[2] It has up to 2.5 mm black circular to slightly polygonal spots that are the fruiting bodies (apothecia), slightly sunken into the main nonfruiting body part (thallus).

[2] It grows on siliceous boulders in very dry climates of western North and South America, where it is usually the most common member of its genus.