That ambiguity is the point. Measuring just 0.6 metres high, 0.24 metres wide, and 0.07 metres thick, it is an easy thing to walk past, and scholars have been cautious about what exactly it is. A defaced stone cross is the working description, meaning a cross whose carved or incised decoration has been worn or damaged to the point where its original form is uncertain. What distinguishes this slab is a rounded notch cut into each of its sides, which could suggest the outline of a cross-head, the kind of simple shaping seen on early medieval Irish stone monuments, though here the evidence is faint.

The description comes from A. O'Sullivan and J. Sheehan's 1996 survey of the Iveragh Peninsula, which documented the extraordinary concentration of early Christian remains on Skellig Michael. The monastery on the island, founded sometime in the sixth or seventh century, was home to a small community of monks who built their dry-stone cells without mortar and buried their dead in the enclosure that now holds this slab. The Monks' Graveyard is one of several distinct areas within the monastic complex, and the stones that mark it range from clearly recognisable grave slabs to ambiguous fragments like this one, worn by salt air and centuries of exposure. The island, about twelve kilometres off the Kerry coast, was inhabited by monks until sometime in the twelfth or thirteenth century, and what they left behind is unusually intact for its age, largely because remoteness served as a kind of preservation.