The stone is roughly 1.36 metres tall and only 0.08 metres thick, and on one face, deeply scored using a pock technique in which designs were pecked into the surface, possibly then rubbed smooth, a prehistoric hand arranged spirals, chevrons, and serpentiform lines across almost the entire surface. The lower third has lost a thin lamina, taking part of the design with it, but what survives is clear and detailed: a horizontal zig-zag across the top, three groups of V-shaped marks descending the left edge, three clockwise spirals at the centre, and a double zig-zag down the right that dissolves into a loose, snaking line near the base.

The stone was unearthed around 1880 during field clearance in the townland of Glen on Cape Clear Island, one of Ireland's most southerly inhabited points. At some stage after its discovery it was moved to neighbouring Sherkin Island, where it lay unrecognised until 1945. It was subsequently presented to University College Cork and eventually placed in the Cork Public Museum. Archaeologist M. J. O'Kelly, writing in 1949, was the first to describe it in detail and to place it firmly within the passage tomb tradition, noting close parallels with carvings at Newgrange, at Bryn Celli Ddu in Wales, and at Gavrinis in Brittany. Passage tomb art is the decorative vocabulary associated with the megalithic burial monuments built across Atlantic Europe during the Neolithic period, roughly five thousand years ago, and the Cape Clear stone fits squarely within that tradition. A passage tomb recorded to the south-east on Cape Clear Island may have been its original context, though the connection remains probable rather than proven.