Roughly square in plan, about two metres a side and barely half a metre high, it has a largely flat upper surface that would have made it serviceable as an improvised altar. During the Penal Laws, the period broadly spanning the late seventeenth and eighteenth centuries when Catholic worship was suppressed in Ireland, priests celebrated Mass outdoors at rocks like this one, often in remote spots where a congregation could keep watch for approaching authorities. The landowner's tradition holds that this boulder served exactly that purpose.

The surface, however, tells a more complicated story than penal-era worship alone. Towards the north-eastern corner, lines of possible pickmarks run alongside three natural-looking hollows, and elsewhere on the rock there are more hemispherical depressions, at least two of which appear to be cupmarks, small rounded hollows deliberately ground or pecked into stone that are associated with prehistoric rock art across Ireland and beyond. These measure between four and seven centimetres in diameter and seven to ten millimetres deep, and one retains at least six pickmarks around its rim. That places the boulder in a broader landscape of prehistoric activity: the rock art site at Rossacoosane lies only 700 metres to the north-east. Adding a further puzzle, the south-eastern end of the boulder bears two inscriptions, one deeply and carefully carved, the other shallowly incised, and both read simply 'money'. Whether these mark a hiding place, record a transaction, or reflect something else entirely is not known. The boulder sits at around 150 metres above sea level on sloping ground, with Kenmare Bay visible to the south-east on a clear day.