The piece is made from garnet mica-schist, a local metamorphic rock with a faintly glittering surface, and it tapers slightly toward the top in the manner typical of early Irish cross-slabs. What makes it unusual is the density and care of its decoration relative to its modest size: two distinct compositions, one on each face, worked in relief into stone that was eventually buried in rubble and only recovered during excavation.

The slab was found during the excavation of an early medieval monastery on High Island, known in Irish as Ardoileán, a small and exposed island off the Connemara coast in County Galway. It had been deposited in rubble cleared from Cell B, a clochan or small dry-stone beehive hut, situated to the east of the island's church. One face displays an expansional cross, a form in which the arms broaden toward their ends, finished with D-shaped terminals; the lower terminal may once have enclosed a triquetra, a three-cornered interlace motif associated with early Christian iconography. Raised bosses appear in the upper quadrants of the cross, and at the upper angles pairs of bosses are connected by C-scrolls or peltae, the latter being a curved shield-like motif drawn from classical ornament and widely adopted in Insular art. The reverse face carries a second expansional cross, though only the left and top terminals remain clearly legible, and the central field is lozenge-shaped rather than square. The slab was catalogued by Ian Fisher, with later revisions by Scally and Maddern, as part of a broader excavation report published in 2014.

The slab is no longer visible at the spot where it was found. It has been moved to the Office of Public Works depot on the island, where it is kept rather than displayed in situ. High Island itself is uninhabited and access requires a boat from the Connemara mainland, typically from Cléggan.