Slag is the glassy waste left over from smelting metal, and vitrified stone, rock that has been fused or part-melted by intense heat, are the kinds of residues that accumulate around sustained industrial furnace work. Together they mark this unremarkable-looking ruin as the remnant of something once considerably more ambitious.

A scholar named McCracken, writing in 1957, referred to a "large works" operating on this site during the seventeenth or eighteenth century. The Ordnance Survey's first edition map, produced in the nineteenth century, recorded an old furnace here as part of a wider complex, suggesting that by the time the surveyors arrived the site was already a memory of something earlier. Ireland had a number of ironworking operations during that period, many of them dependent on local timber for charcoal and on proximity to water for power and transport, and the location at the head of a harbour would have made practical sense for moving materials in and out. What ore was processed here, and by whom, the surviving evidence does not say with any certainty.