What makes the Derrygarrane stone worth seeking out is precisely that weathered quality: the motifs are still traceable, but only just, which gives the encounter a particular quality of attention. This is prehistoric rock art at the edge of legibility.

The boulder is a substantial thing, roughly 2.3 metres along its longest axis and rising to about 66 centimetres at its western end, with two natural fractures running across it that complicate any first reading of the surface. The decorated portion, facing gently eastward, measures around 1.4 metres by 0.4 metres and carries a small but varied collection of motifs. Cup-and-ring marks, the most characteristic form of prehistoric Atlantic rock art in Ireland and Britain, appear here in two varieties: one complete example with a single encircling ring, and one where the ring survives only partially. Cup-and-ring marks are exactly what they sound like, a shallow circular depression, the cup, surrounded by one or more carved concentric rings, though what they meant to the people who made them remains genuinely unknown. Alongside these sit two plain cupmarks, simple rounded hollows with no rings, and two linear grooves, one of which bends eastward at its lower end in a gentle curve. The stone is positioned on the northern side of a low hillock, with an open spread of bogland visible to the north and north-west, and the hill of Knocklomena clear on the northern horizon.

The boulder lies on the southern bank of a small stream that feeds into Lough Fadda and eventually the Kealduff River. A stone wall topped with post-and-wire fencing runs a few metres to the south-west, with a second fence line not far beyond. These modern boundaries are useful reference points once you are in the vicinity, though the approach across open mountain heath requires patience and suitable footwear.