The "elegant sunburst lichen", Xanthoria elegans, on rock, Yukon Territory. The Haisla and Hanaksiala in British Columbia used this lichen as a pigment for face paint. It is easy to confuse this lichen (common in western North America) with some of the lobate species of Caloplaca, especially Caloplaca ignea. A quick test is to gently peel up the edge of a lobe; if it can be removed from the rock without falling apart, it's the Xanthoria.
Photograph copyright Stephen/Sylvia Sharnoff