This is a bullaun stone, and that bowl-shaped depression is the detail that matters. Roughly circular, about thirty centimetres across and ten centimetres deep, it was not made by weather or accident.

Bullaun stones are found across Ireland, typically associated with early medieval ecclesiastical sites, though the full story of their use remains genuinely unclear. The word is thought to derive from the Irish bollán, meaning a rounded hollow. Some were likely used for grinding, others may have held water for ritual purposes, and many accumulated folk traditions over the centuries, with the water that gathered in their bowls credited with healing properties. This particular example is a subrectangular boulder measuring roughly 0.7 metres by 0.57 metres, and standing about 0.3 metres high, modest in scale but carefully placed, or perhaps carefully noticed, at the foot of a gentle slope. Whether any formal site, church, or settlement was ever associated with this stone in Garraun is not recorded, which is itself a not uncommon situation; many bullauns have simply outlasted whatever human context originally gave them meaning.