The stones that form its walls were once part of a single large sandstone boulder, roughly three and a half metres long, whose upper surface had been carved, at some point in prehistory, with at least sixty-five individual rock art motifs. That boulder no longer exists as an archaeological site. In the 1950s a dynamite contractor blasted it apart, and its pieces were carted to the nearby townland of Carhoonahone to do the thoroughly practical job of holding back soil and water.

Before it was destroyed, the stone had already had a difficult history. Observers noted as early as 1909 that at least 1.2 metres had been broken from one end before they ever got to study it. What remained, recorded by Cooke in 1906 and later by O'Connell in 1939, was still remarkable: a large earthfast boulder, fixed in the ground to a height of around 0.75 metres, whose decorated upper surface sloped gently upward from both ends toward the centre. The carvings included at least forty-three cupmarks, which are shallow circular depressions pecked into the rock surface and among the most common forms of prehistoric rock art found in Ireland and Britain, along with twenty-one cup-and-ring motifs, three examples with three concentric rings, and one with four rings. Some of the cupmarks were connected by radiating grooves. The largest single motif measured about 0.3 metres across. A handful of other hollows on the surface may have been natural rather than carved, though the distinction is not always easy to establish with weathered sandstone.

The precise location of the well into which the fragments were built is not known, and it is unclear whether it is still in use. The field where the boulder once lay, on the north-facing slope of the Knocknafreaghaun ridge with open views toward the north and east, now holds only the absence of the thing that was there.