The boulder is roughly two metres by two metres and stands about a metre high, and it is the westward-facing upper surface, fractured heavily across its width, that holds the carvings. They are easy to miss, and the lichen does not help.

The markings belong to a tradition known as prehistoric rock art, and the dominant motif here is the cup-and-ring mark, a form found across Atlantic Europe and the British Isles, typically dated to the Neolithic or early Bronze Age. A cup-and-ring mark is exactly what the name suggests: a circular depression, or cup, cut into the rock surface and surrounded by one or more incised rings. At Derreeny, the east side of the fracture carries three such marks, ranging from eight to twelve centimetres in diameter, alongside a smaller cupmark of four centimetres. There is also a more irregular form, whose groove functions simultaneously as part of the enclosing ring of one cup-and-ring and as the boundary of another, a kind of overlapping or shared geometry that gives the composition an oddly intricate quality. A further cupmark, also four centimetres across, sits below the fracture line itself. The site was identified and recorded by Aoibheann Lambe in March 2023, with a separate low upright carved stone noted approximately ten metres to the north, suggesting the area may repay further attention.