The mound is modest, rising only to about three-quarters of a metre, and measures roughly seven metres by six, but its shape and contents give it away immediately to anyone who knows what they are looking at: this is a fulacht fia, one of the most common yet least explained monument types in the Irish landscape.

A fulacht fia, sometimes called a burnt mound, is the accumulated debris of repeated prehistoric cooking, or possibly bathing or industrial activity. The typical method involved heating stones in a fire until they were intensely hot, then dropping them into a water-filled trough to bring the liquid to boiling point. The stones shattered in the process and were discarded, building up over time into the characteristic horseshoe or crescent shape seen here. The charcoal-enriched soil mixed through the mound at Coonane is the residue of those fires, and the heat-shattered stones are the spent fuel, in a sense. The site's position close to a stream was not incidental. The watercourse that winds around the mound from west to east would have supplied the necessary water, though it may also have caused some erosion to the mound over the centuries. Most fulachta fiadh date to the Bronze Age, roughly 1800 to 800 BC, and they appear in their thousands across Ireland, particularly in Cork and Kerry, often tucked into low-lying or waterside ground exactly like this terrace above the stream at Coonane.