They appear as low, horseshoe-shaped mounds, typically found near water, and are thought to date mainly from the Bronze Age, roughly 1500 to 500 BC. The working theory is that they served as outdoor cooking sites: stones were heated in a fire and then dropped into a trough of water to bring it rapidly to the boil, leaving the burnt and shattered rock to accumulate into the distinctive mound we see today. The one recorded on Mountain Common in County Mayo is one more mark in that long, largely anonymous pattern of ancient domestic activity.

Beyond its classification and location, the specific details of this particular site remain largely unrecorded in publicly available sources. What can be said is that Mayo has a significant concentration of these monuments, spread across bogland and common ground where the waterlogged conditions have both preserved the mounds and, for centuries, discouraged the kind of intensive agriculture that might otherwise have destroyed them. Mountain Common, as the name suggests, is the sort of open, marginal ground where fulachtaí fia tend to survive best, away from the plough and the field boundary. The site exists, it has been noted, and somewhere beneath or beside that characteristic mound of fire-cracked stone there is almost certainly evidence of the trough and hearth that once made it function.