The lichen was first formally described as a new species in 1868 by the Finnish lichenologist William Nylander, based on collections made from coastal Angola.

[4] Buellia subalbula has a crustose thallus, which is thin to thick and often forms distinct circular patches.

The thallus texture ranges from smooth and continuous in thinner forms to cracked and segmented (rimose-areolate) in thicker ones.

The margins of the thallus are bordered by a prothallus, which is noticeably blackened to pale grey, and in some cases, white but less distinct.

The exciple, the layer surrounding the disc, is composed of narrow hyphae with a unique pigmentation that turns bluish-green under certain conditions.

Beyond this primary region, there have been only a handful of recorded occurrences: a singular collection was made in Namibia, another in Bolivia in South America, and one specimen has been documented in Western Australia.