It is only about two metres long, and its interior narrows to less than a metre in width and barely sixty centimetres in height. Yet this cramped opening in the hillside is among the oldest known copper mines in Ireland, worked not by industrial-age miners but by people using stone mauls, the rounded hammerstones that Bronze Age communities used to pound and fracture ore-bearing rock from the living cliff face.

When archaeologists excavated the waterlogged peat that had sealed the mine's entrance, they recovered fragments of wood and those stone mauls from the primary sediment layer. Radiocarbon dating of the wood produced two closely agreeing results, placing the activity somewhere around 1200 to 1300 BC, well into the Irish Bronze Age, a period when copper was being extracted and alloyed with tin to produce the tools and weapons that defined the era across Atlantic Europe. The working was driven at a bearing of roughly 230 degrees into the scarp, a near-horizontal tunnel following the ore rather than sinking vertically. There are no visible spoil dumps outside the entrance today; the excavated material was most likely washed or tipped into the east-west valley immediately below, where it has long since blended into the landscape. The site sits just south of the Rathcool and Mountgabriel townland boundary, in an area of west Cork that, around the shores of Bantry Bay and along the Mizen Peninsula, preserves a remarkable concentration of prehistoric mining evidence.