Carved into the stone is a ringed Greek cross rendered in two incised lines, and at its head sits a human face, oval in outline, with almond-shaped eyes, a straight nose, and a mouth held slightly open. A ridge of stone defines the brow. This type of carving is known as a face cross, a relatively rare variant of the early medieval cross-slab tradition in which the cross itself is given a human presence, the intersection of sacred geometry and portraiture compressed into a few centimetres of worked sandstone.

The slab comes from Mason Island, or Oileán Máisean, a small island off the Connemara coast in County Galway. It was one of two cross-slabs associated with a leacht near the island's early church; a leacht being a low, typically cairn-like devotional monument, often connected with the commemoration of saints or the performance of penitential ritual. The slab was recorded by Higgins in 1987, and the grouping it belongs to, two cross-slabs positioned around eight metres to the south-west of the church, points to a concentrated pocket of early Christian activity on what is now a sparsely inhabited island. The sandstone itself is local in character, subrectangular in shape, and despite its damage retains the carved detail with enough clarity that the face remains legible.

The slab is no longer on Mason Island. It is currently held by the National Museum of Ireland in Dublin, where it has been removed for preservation. Visitors to the island today would find the leacht and the church remains, but the cross-slab itself is safest encountered in the museum's collections.