The object in question is a cross-slab, a type of early medieval marker used at penitential stations where pilgrims would pray, kneel, and move through prescribed circuits of devotion. This particular example, roughly 72 centimetres tall and cut from garnet mica-schist, the glittering metamorphic rock native to the Connemara region, is shaped into a short-armed cruciform form, so the slab itself reads as a cross before you even consider what is carved upon it.

The decoration is dense and carefully considered. The northern face carries a Latin cross rendered in high relief, framed within a band that encloses a double-banded cross, a layering of forms that rewards close attention. In the top terminal sits a triquetra, the three-cornered interlaced motif associated with early Christian art across Ireland and Britain, and there is a raised boss in the upper left quadrant. Turn the slab to its southern face and the carving is more worn, a linear cross set within a double roundel, its terminals finishing in small crosslets. The surviving left arm carries yet another linear cross, also with crosslet terminals. This accumulation of crosses on a single object is characteristic of the early Irish monastic tradition, where repetition of the sacred symbol was itself a form of prayer. High Island, known in Irish as Ardoileán, was the site of a significant early monastery, and scholars including White Marshall and Rourke, writing in 2000, have documented the island's collection of carved stones as among the more intact early Christian assemblages on the west coast. The slab is now held at the Office of Public Works depot in Athenry, having been removed from the island for its protection.