The opening, roughly 3.8 metres wide and 1.8 metres tall, leads into a low flooded tunnel barely a metre high inside, its walls worn into a smooth concave curve that archaeologists recognise as the signature of fire-setting, a Bronze Age technique in which fire was lit against the rock face to crack it, before the loosened material was worked away by hand. It is a compact, easily overlooked feature of the landscape, and yet it represents one of the earliest known episodes of organised copper extraction in Ireland.

The mine came to wider attention in 1854, when local landowner Richard Hungerford investigated the workings. Inside, he found stone mining mauls, the heavy rounded hammerstones used to pound ore from the rock, along with a cache of twelve polished stone axes. The discovery was noted by Caulfield in 1880. A charcoal sample later taken from the mine was radiocarbon dated to 3400±30 BP, placing activity here in the Bronze Age, roughly the middle of the second millennium BC, at a period when the Mizen Peninsula and the wider Munster coastline were among the most intensively mined copper-producing landscapes in Atlantic Europe. Outside the entrance, a spoil mound measuring around 13 metres by 7 metres survives, along with a narrow trench dug by antiquarian investigators, 13.5 metres long and just over a metre wide, cut presumably to examine what lay beneath the accumulated debris of the mound itself.