The decorated surface is barely knee-height at its tallest point, irregular in shape, and tilted very slightly to the north-east. What it holds is a concentrated language of prehistory: cup-and-ring motifs, where a small circular hollow is surrounded by one or more carved concentric rings, scattered cupmarks of varying sizes, radial grooves cutting outward from central cups, and at least one small grid pattern formed by linear grooves crossing one another. Two particularly complex motifs sit at the southern end of the surface, each consisting of a cupmark with radial grooves set within four or five loosely arranged rings, with a further cup-and-ring attached to the outermost of those rings. The whole decorated area measures roughly 1.8 metres by 1.3 metres, which makes it a dense concentration rather than a sprawling composition.

Rock art of this kind, produced by pecking or picking designs into stone surfaces, is found widely across Atlantic Europe and is generally associated with the Neolithic or Early Bronze Age, though its purpose remains genuinely unresolved. The Coomasaharn complex sits in an area of blanket bog at around 168 metres above sea level, and immediately to the west of this particular outcrop there is a pre-bog field wall, meaning the wall predates the spread of the bog across the landscape, itself a process that began in the post-Neolithic period. The proximity of that wall to the carved rock is suggestive, though exactly what it suggests is harder to say. The site was documented by A. O'Sullivan and J. Sheehan in their 1996 archaeological survey of the Iveragh Peninsula, published by Cork University Press, and a later survey compiled by Alison McQueen and Vera Rahilly found the rock noticeably changed, with motifs considerably fainter and some features obscured by encroaching vegetation, surface water, and bog growth. Several cupmarks that were once clearly defined have been worn to near-invisibility, and two that may originally have carried concentric rings are now too weathered to confirm.