I am way in above my head here and will gladly encourage corrections or suggestions concerning my identification.
Traveling through Nevada (at Grimes Point Archeological Site) and at the Great Basin National Park, Leonard and I saw bright blue lichen – not greyish, but a definite blue. I was enchanted with the color and took too many pictures, none of which do the blue justice.
Lichen are evolutionary ancient composite organisms composed of a fungus and a photosynthetic partner (green algae, cyanobacteria or both). Both partners grow together in a mutually controlled symbiotic relationship.
I believe these specimens are Rhizocarpon disporum or single-spored map lichen. This species is usually described as dull grey to grey-brown, but there is much variation in the color. Known as crustose lichen, the thallus (vegetative body) is a crust-like growth clasely attached to the substrate over the entire lower surface. The fruiting body (ascocarp) is a black disk. Cracks in the thallus are black.
Single-spored map lichen are cosmopolitan growing not only in semi-arid regions of Western North America, but also in Greenland, Europe, South America, Antarctica, New Zealand and Australia. Their habitat is siliceous rocks, including sandstones.
Rhizocarpon disporum is characterized by having only a single spore formed in each ascus (structure where the spores are formed). This species is often classified with R geminatum, which has more than one spore per ascus.
I love the color of this fascinating lichen.