Found in their thousands across the country, they typically consist of a mound of fire-cracked stone and charcoal, often arranged in a horseshoe or kidney shape around a central trough and hearth. The working theory is that stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil, though for what purpose, cooking, bathing, textile processing, or something else entirely, remains unresolved. What makes the example at Coolboy quietly strange is that the excavation produced none of the usual evidence that might at least confirm the basic mechanics of the process.

When road development for the Arklow bypass prompted archaeological investigation, excavator Colin D. Gracie uncovered a horseshoe-shaped spread of burnt material roughly five to six metres in diameter. Despite the spread conforming to the classic form of a burnt mound, neither a hearth nor a trough was identified anywhere within or beneath it. The only artefact recovered was a single flint flake found on the surface of the burnt deposit. Flint, not naturally abundant in County Wicklow, indicates human activity and a degree of intent, but a lone flake offers little in the way of narrative. The site yielded its shape and almost nothing else, leaving open the question of whether the usual associated features were simply not preserved, were located elsewhere, or whether this particular deposit represents something at the margins of what we typically call a burnt mound.