It measures roughly 8 metres wide and only 1.6 metres high, driven just 1.4 metres into the rock. What makes it quietly remarkable is what it represents: a primitive copper mine, cut directly into a sedimentary copper-bed, and quite possibly worked using one of the oldest extraction techniques known to archaeology.

The rock-face inside the working carries faint traces of malachite, the vivid green copper carbonate mineral that ancient prospectors used to locate ore-bearing seams. More telling is the smooth, concave profile of the rock surface, which researchers have suggested may be the result of fire-setting, a technique in which fire was lit against the rock face to heat it rapidly, then water or cold air applied to cause the stone to crack and spall away, making it easier to work with simple tools. A shallow infill at the mine entrance may be concealing a small spoil-dump beneath, and a ruined stone wall survives to the south-east of the working. The site was discussed by O'Brien in 1987, and the combination of the malachite mineralisation, the fire-setting profile, and the sedimentary copper-bed all point to activity that predates any industrial-era mining. Exactly when the mine was worked remains uncertain, but the techniques are consistent with prehistoric or early medieval copper extraction of the kind documented at other sites along the Iveragh Peninsula.