The boulder is modest in size, under a metre across in any direction, yet its decorated face holds seventeen cupmarks, several of them connected by grooves, along with cup-and-ring motifs and a dense concentration of around a hundred individual pickmarks gathered in the northwest corner of the surface. Cupmarks are exactly what they sound like: small, shallow, circular depressions pecked into rock, found across prehistoric Europe and Ireland with a frustrating absence of any written record of their purpose. Cup-and-ring motifs add one or more concentric rings around the central cup, sometimes with a groove running outward like a channel. At Derreeny, the space between cup and ring on at least two of the motifs has been further worked with pickmarks, suggesting these were not casual impressions but carefully considered compositions.

The boulder lies at about 165 metres above sea level, tucked between a parallel pair of drystone walls on a short northwest-facing slope, with a clear view towards the Ballaghbeama Gap. That orientation is worth noting: the Gap is a dramatic natural pass through the Macgillycuddy's Reeks, and whether or not the prehistoric carvers were conscious of the relationship between the stone and the landscape beyond it, the alignment feels deliberate to anyone standing there. The rock itself is smooth and unfractured sandstone, its surface carrying a slight northwest tilt that has left the markings weathered and faint. A survey of the Iveragh Peninsula compiled by A. O'Sullivan and J. Sheehan, published by Cork University Press in 1996, recorded the site, and a later detailed survey by Alison McQueen and Vera Rahilly added the more precise measurements and description of the pickmark clusters and curvilinear grooves that distinguish this boulder from a simpler, less worked example.

The site sits in heath pasture between those drystone walls, and the faintness of the carving means that raking light, particularly on a low-sun day in spring or autumn, gives the best chance of reading the full composition across the stone's surface. The linear and curvilinear grooves running off-centre to the northeast of the decorated face are easy to miss entirely in flat or overcast conditions.