It is classified as a holy or saint's stone, and what makes it particularly unusual is that its sacred status is rooted not in any abstract reverence for ancient rock but in a very specific, almost novelistic story about a local patron saint.

The stone is associated with St. Fanahan, patron saint of Mitchelstown and the surrounding parish of Brigown. According to the legend recorded by Power in 1980, Fanahan was taken prisoner in Clonmel and chained to two millstones, presumably as a means of keeping him bound and immobile. He was, however, granted the strength to roll both stones back towards Brigown. One broke along the way. The second, the one now lying in the river roughly 450 metres to the east-south-east of the early ecclesiastical site at Brigown, is said to be where the saint was finally set free, released by a stranger who appeared on a white horse. The stone itself is likely a runner stone from a horizontal mill, the kind of simple grain-milling structure common across early medieval Ireland, in which a flat stone rotated horizontally over a fixed lower stone, driven by a water wheel beneath. Its size and form are consistent with that function, which gives the legend an odd, grounded quality: this is not a mysterious monolith of unknown origin, but a workaday object pulled into the orbit of the sacred.

The stone lies in mid-stream near Ballynamona Bridge, close to the Brigown ecclesiastical site, which sits not far from Mitchelstown. Visitors approaching from the bridge should look towards the southern bank of the watercourse, where the stone remains in situ, partially submerged depending on water levels.