This is a bullaun stone, a type of ancient carved rock found across Ireland, typically bearing one or more rounded depressions ground into the surface, the purpose of which remains debated. Some are associated with early Christian sites and ritual use; others appear to predate Christianity entirely. The island in question, known in English as Inishcaltra or Holy Island, sits in Lough Derg on the Clare shore and is one of the more remarkable early medieval monastic sites in the country, which makes the presence of such a stone entirely fitting, even if the stone itself refuses to be found.

The most precise description of this bullaun comes from the antiquarian R. A. S. Macalister, writing in 1916 to 1917. He recorded a stone measuring roughly 0.78 metres by 0.53 metres by 0.43 metres, with an oval depression approximately 0.43 metres long, 0.3 metres wide, and 0.12 metres deep. It was noted on the Ordnance Survey six-inch map of 1920, placing it towards the island's north shore. When the site was visited in July 2015, the vegetation had grown so densely that the stone could not be located at all. It has not vanished exactly, but it is presently hidden, somewhere beneath the bramble and growth, waiting.