The slab standing there now is a replica, a quiet admission that the real thing has been removed for safekeeping, held at an OPW depot in Athenry. The original, carved from garnet mica-schist, a metamorphic rock with a faintly glittering surface, measures just under sixty centimetres tall and tapers towards the top. It was found in position as the footstone of what researchers have called pseudo Grave 7, in the northern half of the island's small graveyard, to the east of the early medieval church.

The decoration is confined to the east face only. Incised into the stone is a cross set within a double ring, and where the arms of the cross meet the outer ring, each arm splits into a pair of oblique terminals, a forked flourish that gives the design an almost heraldic precision. Cross-slabs like this, flat stones incised with a cross rather than carved in full relief, were a common form of early Christian grave marker in Ireland, though this one was probably reused from an earlier context before being set as a footstone. A closely comparable slab can be seen on the grave immediately to the south, suggesting the graveyard once held a set of related markers. Fisher's 2014 study documented this slab alongside the wider monastic complex on the island, and it also appears in the 2000 survey by White Marshall and Rourke.