Half of the bottom stone and all of the broken top stone survive, each about 0.7 metres in diameter and 0.25 metres thick. Together they point strongly to the former presence of a horizontal mill on this spot.

A horizontal mill, sometimes called a Norse or tide mill in different contexts, is one of the oldest and simplest milling technologies found across Ireland and the wider Atlantic fringe. Unlike the more familiar vertical waterwheel, a horizontal mill uses a wheel laid flat beneath the millhouse, with water directed through a narrow chute to strike the paddles and spin the upper millstone directly above. No gearing is required, which made these structures relatively easy to build and maintain in remote or lightly resourced communities. They were common throughout early medieval Ireland, and traces of them tend to survive as little more than earthworks, stone fragments, or the faint channel of a diverted stream. The Cloonamore stones are a typical remnant of this kind, modest in scale but suggestive of a community that once had reason to grind grain on the island.