On High Island, a remote and wave-battered outcrop off the Connemara coast, a carved stone slab was discovered lying face-down within the lowest course of masonry beneath the church altar, built into the structure rather than displayed by it. Whoever incorporated it had turned it inward, its decorated face pressed against rubble, preserving by accident what might otherwise have been worn smooth by centuries of weather.

The slab, a roughly rectangular piece of garnet mica-schist measuring 0.67 metres tall and 0.53 metres wide, bears on one face a grooved linear cross with forked terminals, the arms splaying outward at their ends in a style associated with early Christian stonework in Ireland. The same decorative form appears on another cross-slab found near the holy well elsewhere on the island, suggesting these stones belong to a coherent, if now fragmented, tradition of carving from the island's monastic period. The slab had been broken obliquely across its lower left corner before or during its reuse in the altar, and flaking to the stone has left the lower terminal of the cross incomplete, so whether it once matched the forked ends of the other arms cannot now be determined. The stone is now held at the Office of Public Works depot in Athenry, County Galway, removed from the island for safekeeping.