This is a bullaun stone, a type of boulder or outcrop with one or more cup-shaped hollows ground into its surface, found widely across early medieval Irish ecclesiastical sites. Their exact purpose remains debated, but they are generally associated with ritual or devotional use, and many accumulated secondary objects, such as loose stones, that were turned in the basin as part of local practice.

This particular bullaun is a modest thing physically, roughly 0.6 metres long and only 0.3 metres high, with a basin around 35 centimetres across and 18 centimetres deep. What makes it quietly interesting is its apparent restlessness. The Earl of Dunraven, writing in 1877, recorded it at the west gable of St. Caimin's Church, the early medieval church that still stands on the island. By 1984, when researcher McNamara documented it, the stone had migrated to the north gable. It now sits approximately 30 metres north of the church altogether. Whether these moves were deliberate, incidental to other works on the island, or the result of repeated casual repositioning over generations is not recorded. McNamara also noted a round blue sandstone weighing around five kilograms sitting inside the basin, a detail that suggests ongoing ritual significance well into the modern period. That stone is no longer there.