Known in Irish as Carraig an Aifrinn, meaning the Rock of the Mass, it is an oval, flat-topped boulder measuring roughly 75 centimetres by 60 centimetres, and standing just 70 centimetres from the ground. On its southern face, a carved cross, modest in scale at 28 centimetres tall and 18 centimetres wide, marks it out as something more deliberate than a field stone. A concrete apron, about a metre and a half across, now surrounds its base, and a cement repair holds together a crack that had opened in the rock at some point.

Mass-rocks are the physical residue of the Penal Laws, a body of legislation introduced in Ireland in the late seventeenth and early eighteenth centuries that stripped Catholics of property rights, access to education, and, critically, the freedom to practise their religion openly. Priests were banned or required to register under severe restrictions, and the celebration of Mass was driven out of churches and into the landscape itself. Communities gathered at remote or sheltered spots, often with a lookout posted nearby, and used whatever flat surface was available as an altar. The Tawly stone, with its incised cross, is a relatively formalised example; many mass-rocks are simply unremarkable field boulders whose significance is carried in local memory rather than in any marking on the stone itself. That this one was given a name, Carraig an Aifrinn, and that the name has survived, suggests it held particular importance for the local community.