It is, in fact, the remains of a fulacht fia, one of the most common yet consistently puzzling monument types in the Irish landscape. These are ancient cooking sites, typically Bronze Age in date, where stones were heated in a fire and then dropped into a water-filled trough to bring it to a boil. The process shattered the stones with thermal shock, and over repeated use, the broken, fire-cracked fragments accumulated into the characteristic mound shape that survives today.

The Glenacarney example measures roughly seven metres on its longer north-northeast to south-southwest axis and four metres across, with an opening facing east. The mound is composed of heat-shattered stones and charcoal-enriched soil, the blackened earth being a reliable indicator of sustained burning over time. It came to light not through any deliberate excavation campaign but during archaeological monitoring carried out ahead of ground preparation works for afforestation, work recorded by O'Mahony in 2005. The site's waterlogged setting is itself characteristic; fulachtaí fia are almost always found near a reliable water source, whether a stream, a spring, or naturally boggy ground, since the whole process depended on a ready supply.