Set into the south wall of the grotto, the smooth unfractured sandstone measures just over half a metre across and barely twelve centimetres tall, yet its decorated face is surprisingly busy. To the left sit two horseshoe-shaped carvings, one slightly larger than the other, their outlines painted white. To the right, an elaborate curvilinear pattern fills the remaining surface, resembling, to those who have looked closely at it, a patchwork of fields seen from above, with a wavy upper register that suggests a range of low hills. A third horseshoe motif appears at the northern end of this grid. One of the curving lines terminates in a small cup-shaped hollow. Every carved feature has been painted white, which gives the stone an oddly deliberate, finished quality, as though someone wanted it to be noticed.

What the carvings mean, and who made them, remains genuinely uncertain. Local enquiries have produced no traditions or explanations attached to the stone. Researchers have suggested it is probably not prehistoric rock art in the conventional sense, since that category typically involves open-air outcrop surfaces and a fairly well-understood repertoire of motifs. The style here points instead towards a medieval or post-medieval origin, though no closer date has been established. The stone itself is thought to be ex-situ, meaning it was likely moved from its original location at some point, and may once have formed part of a larger composition alongside at least one other carved stone. That companion piece, if it ever existed, has not been found. The grid-like pattern on the right half is particularly unusual; if it does represent a field system or a landscape, it would place this piece within a small and poorly understood tradition of vernacular carving that sits somewhere between folk art and something harder to name.