These are cupmarks, shallow depressions ground or pecked into rock surfaces during the Bronze Age or earlier, and while their precise purpose remains genuinely unknown, they appear across Atlantic Europe in sufficient numbers to suggest they once held real significance, whether ritual, territorial, or something else entirely beyond modern reconstruction.

The boulder at Glannafeen sits on a west-facing slope and measures roughly 1.8 metres along its northwest to southeast axis and 1.4 metres across, rising about 0.75 metres at its highest point before tilting downward to the west. On its upper surface are two deliberate marks: one circular, about eight centimetres in diameter and two centimetres deep, and one oval, measuring twelve by seven centimetres and three centimetres deep. The stone also carries several naturally occurring depressions, which makes the identification of genuine cupmarks a matter of close attention. The two carved hollows are distinguished by their regularity and by the smoothness that sets human work apart from the irregular pitting that frost, water, and time produce on their own.

Lough Hyne itself adds a particular character to the setting. It is a sea lough connected to the Atlantic by a narrow channel, and its shores shift between exposed rock and dense coastal scrub. The slope where the boulder lies, south-facing toward the water and west-facing into the prevailing weather, would once have been open ground. The ferns and briars that now cover it are relatively recent growth in archaeological terms, and the cupmarked stone would have been far more visible to whoever passed this way in prehistory than it is to anyone searching for it today.