It was not found by digging but by listening, in a manner of speaking, to the ground itself.

A magnetic gradiometer survey, a non-invasive technique that measures variations in the earth's magnetic field to detect buried features, picked up a subcircular anomaly roughly 20 metres east to west and 10 metres north to south, with a notably strong magnetic susceptibility. That kind of signal is consistent with a burnt mound, also known in Irish as a fulacht fia. These are among the most common prehistoric monuments in Ireland, typically dating to the Bronze Age, and they represent the accumulated debris of a cooking or industrial process involving the repeated heating of stones and their subsequent dumping when cracked. Over time the discarded material builds into a distinctive mound, often horseshoe-shaped in plan, usually found close to a water source. The heat-shattered stone produces a strong magnetic signature in the soil, which is precisely what the Rosspile survey detected. The feature was identified as part of a wider geophysical survey carried out in 2020 and documented by Nicholls that same year.