It is roughly ten metres across and about half a metre high, modest enough that a casual observer might take it for a natural rise or a dumped heap of old soil. What it actually represents is a fulacht fia, one of the most common and yet most quietly puzzling monument types in the Irish countryside.

A fulacht fia is, in essence, the burnt and waterlogged remnant of an ancient cooking or processing site. The typical method involved heating stones in a fire and dropping them into a water-filled trough to bring it to the boil; the cracked and shattered stones, discarded again and again over time, gradually accumulated into the horseshoe-shaped or oval mounds that survive today. Most are Bronze Age in date, though some examples span a wider period. The Carrignamuck example has not escaped the pressures that have reduced or destroyed so many of its kind across Ireland. It has been partly cut by a drainage channel and further reduced by ploughing, both common hazards for low-lying earthworks in agricultural land. What remains is an overgrown spread of burnt material, surviving largely because it sits at the margin of the field rather than squarely within it.