It measures just one metre tall and is barely five centimetres thick, cut from mica-schist, a local metamorphic rock with a faintly lustrous, layered texture. The decoration is minimal: a single incised line running the length of the shaft, and where the arms meet, a Greek cross, meaning one with four arms of equal length, lightly scored into the stone.

The cross was catalogued by Patrick Healy in 1972 as part of a supplementary survey of ancient monuments at Glendalough, an unpublished report prepared for the Office of Public Works. Healy assigned it the number 214 in his survey, and his description remains the principal record of the object. The Greek cross motif, simple as it appears, is a form with early Christian associations across Ireland, and its presence here connects Brockagh to the broader monastic landscape of Glendalough, the valley in County Wicklow that grew into one of the most significant ecclesiastical sites in early medieval Ireland. Whether the cross originally marked a boundary, a grave, or some other sacred point in that landscape is not recorded.