Not a dune at all. On the high quartzite summits of the Wasatch, lightning strikes bare rock rather than sand, and what it leaves is a rock fulgurite: a thin glassy skin or spatter fused onto the outcrop where the current entered, sometimes with the rock around it shattered. Mount Timpanogos, Mount Baldy, Broads Fork West Twin and Mount Raymond all carry them, because an exposed quartzite ridgeline in an afternoon storm is close to the most strike-prone ground there is. A Utah Geological Survey geologist makes the practical point directly: these are welded to the mountain, and the tools you would need to take one are exactly the tools you must not be using inside a state or national park. Go and look at it on the rock.
Rock fulgurite
Other places on the map within a couple of hours.
