Pleopsidium flavum (gold cobblestone lichen) is a distinctively colored, bright lemon-yellow to chartreuse crustose lichen that grows in high elevations (montane to alpine) on vertical or overhanging hard felsic rock (e.g. granite) in western North America. Its thallus grows in a circular outwardly radiating pattern (crustose placoidioid), with 1mm wide lobed edges. It was formerly classified as Acaraspora chlorophana. It is in the Pleopsidium genus of the Acarosporaceae family.