The rock itself is modest in scale, roughly 3.9 metres east to west and less than 60 centimetres at its highest point, with a hogback profile and a long convex upper surface. What makes it quietly extraordinary is what covers that surface: approximately forty-seven cupmarks, the shallow, roughly circular depressions that form the basic vocabulary of prehistoric rock art, along with twelve cup-and-ring motifs, where a carved circle surrounds a central cup. Several of these rings are penannular, meaning the circle is left deliberately incomplete. From many of the cups and rings, radial grooves run outward and down the slope of the rock, some extending over a metre in length, with a number terminating in further cupmarks. At the highest point of the stone, a double cup-and-ring motif carries the longest single groove on the whole surface, running just over a metre to the east.

Cupmarks and cup-and-ring carvings of this kind belong broadly to the Bronze Age, a tradition found across Atlantic Europe and particularly concentrated in Ireland, Scotland, and northern England. Their purpose remains genuinely unresolved; interpretations range from territorial or astronomical markers to ritual deposits of meaning that we are no longer equipped to read. What distinguishes the Coomasaharn example is both the density and variety of its carved motifs and the deliberateness of its placement. The site commands wide views in multiple directions, overlooking significant landscape features including a lake, a river valley, and several mountain summits. Researchers have suggested that the rock may have functioned as a kind of Bronze Age landscape map, its grooves and cups potentially corresponding to watercourses, settlements, and topographical features visible from that exact vantage point. Whether or not that reading is correct, the choice of location feels considered rather than incidental, and Kealduff Cliff looming to the south-west adds a further sense of the site being framed within, and oriented towards, its surrounding terrain.