The stone is subrectangular, roughly two metres long and just over half a metre high, the kind of solid, unshowy presence that could easily be mistaken for a natural outcrop. But look closely and you will find something older than its most recent use carved into the rock: eleven shallow depressions, likely cupmarks, the term for small, roughly circular hollows ground or pecked into stone surfaces, found across prehistoric Europe and of still-debated purpose. They are enclosed within a rectangular area defined by shallow grooves on two sides, as though someone at some point framed them deliberately, though whether that framing is ancient or later is not recorded.

The stone is traditionally known as a mass-rock, a category of site particular to Ireland's penal era, roughly the late seventeenth and early eighteenth centuries, when Catholic worship was suppressed under the Penal Laws and priests celebrated Mass outdoors, in remote or inconspicuous locations, using a convenient flat stone as an improvised altar. The congregation would gather in fields, on hillsides, or in sheltered hollows, with lookouts posted against the possibility of discovery. This stone in Coorleigh fits the type well: flat-topped, positioned on a slight rise, and set in open pasture where both priest and people could see and be seen. What makes it more complicated is the presence of those possible cupmarks beneath the surface of that tradition. Cupmarked stones in Ireland are typically associated with the Bronze Age or earlier, meaning this particular rock may have held significance across several thousand years and at least two very different belief systems, each leaving its own faint trace.