Near the top of its south-eastern face, a small, crudely incised cross sits almost invisibly against the stone's surface. That kind of marking is not unusual in Ireland; early Christian communities frequently added crosses to older megalithic stones, effectively reclaiming pagan monuments for a new faith without going to the trouble of removing them. What makes the Grassyard stone quietly interesting is how that layering of belief sits on an otherwise unremarkable slab in an unremarkable field.

The stone itself is substantial without being monumental: 1.37 metres high, 1.3 metres wide, and 0.65 metres thick, an upright slab aligned along a north-west to south-east axis. Such orientations in Irish standing stones are sometimes linked to solar or lunar events, though specific astronomical claims for any individual stone require careful measurement and caution. The cross, documented by researcher Christina Fredengren in 2010, is described as barely visible to the naked eye, which raises the question of how many similar markings on similar stones across the country have simply worn away or gone unnoticed over the centuries.