It is a cross-slab, a flat stone incised with a cross, a common enough form of early medieval grave marker in Ireland, but this one has some precise and quietly interesting qualities that repay attention.

When the scholar R. A. S. Macalister surveyed the island in 1916 and 1917, he recorded the slab in the western half of the area known as the Saint's Graveyard and classified it as twelfth-century in type. At that point it was intact, measuring four feet ten inches in length and one foot five inches wide. The cross itself was incised in double lines, meaning each arm was defined by two parallel grooves rather than a single cut, with hollowed angles at the intersections. The arms and head of the cross extended all the way to the edges of the slab, and at the base the lines bent outward at ninety degrees and ran to the edges as well, a formal, almost architectural arrangement. By the time the archaeologist Liam de Paor examined it, the slab had been moved and was sitting in a pile of worked stone beside the graveyard wall, already broken at a slight diagonal across its middle. Only the upper portion now survives, measuring around 0.89 metres. What Macalister saw as a complete slab has since lost roughly its lower third, somewhere between a careful survey and the present day.

The slab lies to the south of the OPW chalet on the island, among other loose stonework. Iniscealtra is accessible by boat from Mountshannon on the Clare shore, and the Saint's Graveyard is one of several ecclesiastical enclosures on the site. The fragment is easy to overlook precisely because it is no longer standing, but the incised cross on the surviving upper portion remains legible if you look for it at ground level.