The entrance has a rounded profile, almost modest, and inside the hanging wall carries a smooth, concave surface produced by fire-setting, a technique in which fire was lit against the rock face to crack it through rapid heating and cooling, allowing the softened stone to be worked away. The tunnel itself is accessible for only about five metres today, partly because it was found flooded when inspected in 1984, but the scale of the spoil dump spread outside the entrance makes clear the original working was considerably more extensive.

This is one of 31 prehistoric copper mines identified on Mount Gabriel, together forming one of the most significant Bronze Age mining complexes known in Ireland. The site was studied in detail by the archaeologist William O'Brien, whose 1994 monograph brought the full extent of the complex to wider attention. Excavation of the semicircular spoil dump outside the entrance, measuring roughly 14 metres north to south and 13 metres east to west and reaching a depth of 1.6 metres, recovered 272 fragments of stone mauls, the rounded hammer stones used to break ore from the rock. A radiocarbon date obtained from oak charcoal found at the site, laboratory reference GrN-13668, returned a result of 3430 plus or minus 30 years before present, placing it firmly in the Bronze Age and suggesting it was broadly contemporary with at least two other excavated mines on the mountain. The sheer number of maul fragments concentrated in a single dump gives some sense of the sustained, organised effort that copper extraction here involved, long before metal tools made the work any easier.