The feature that makes the place particularly absorbing is a leacht, a type of commemorative or devotional stone cairn associated with early Irish monasticism, that excavators found not merely beside the island's drystone oratory but structurally bound up with it, the two built as a single integrated scheme. The leacht ran for 3.6 metres along the northern wall of the oratory, its borders defined by large vertical stones set individually into cut trenches, braced at their bases with smaller stones, and its interior filled with redeposited soil, gravel, and rough stone layers. White quartz stones, a material with long ritual associations in Irish archaeology, covered the top. The whole thing measured only 0.4 metres in height, lower than comparable leachta on Skellig Michael, yet it appeared to excavators to be essentially undisturbed and in its original condition.

Four seasons of excavation between 1992 and 1995 uncovered roughly seventy per cent of the island. Beneath and to the east of the drystone oratory, researchers found evidence of two earlier sod-built structures, possibly also oratories, suggesting the site had gone through several phases of use before the stone building was raised. A radiocarbon date derived from a layer overlying the clay floor of the drystone oratory placed activity there between approximately 640 and 790 AD, firmly within the early Christian period. The oratory itself was conserved in 2001 and 2002. The island's name adds a further layer of uncertainty and interest. Marshall and Walsh noted in 1998 that there is no historical documentation for it and that the origin of Oileán Lócháin is genuinely unclear. One possibility is that Lochán was a saint connected to the island, a reading supported by the appearance of two saints of that name in the Martyrology of Oengus, a calendar of Irish saints written around AD 800, and by the existence of an ecclesiastical site called Killoughane at the far eastern end of the Iveragh peninsula. A rival reading, drawn from nineteenth-century Ordnance Survey notes, translates the name simply as the island of the chaff.