Around 1974, rising water in a steep-sided stream scoured away enough sediment to expose two fragments of an ancient millstone, and shortly afterwards an oak floor of five or six planks emerged from the same bend in the channel. Before anyone could properly document it, another flood came and took the timber away entirely. The stone fragments, at least, were carried to an adjacent field and survived.

What those two pieces represent is a runner stone, the upper rotating disc of a horizontal-wheeled water mill. This type of mill, sometimes called a Norse or tidal mill depending on its setting, used a horizontal wheel set directly in the current to drive the millstone above without any gearing. They were widespread in early medieval Ireland and are often found only through accidental discovery, since most were built largely of timber and have left little in the ground. The Curraghgorm stone, when its fragments are fitted together, measures 0.65 metres in diameter and 0.08 metres thick. A central perforation of roughly 0.1 metres across allowed the drive shaft to pass through, and a concentric lip around it on the upper face helped contain the grain. On the underside, four shallow rind-bar sockets are visible; these would have held the wooden or iron bars connecting the stone to the shaft below. Beyond possible stone facing along the stream banks, no other structural evidence of the mill has been identified.