The earliest artefact yet found in the Killarney valley has been uncovered on Ross Island on the shores of the lower lake by archaeological field-trippers.
The 7,500-year-old Stone Age spear-head knife was found two weeks ago during a field trip by English enthusiasts led by the archaeologist Michael Gibbons.
The implement was found on the lake shore near the ancient copper mines and was handed to Mr Gibbons by Hazel Barter, whose husband had picked it up.
"I nearly fell over. This is a critical piece of the jigsaw and the most conclusive evidence yet that there was a hunter-gatherer presence on the lake," Mr Gibbons said yesterday.
Ross Island, which is connected to the mainland, has come to prominence in recent years due to renewed interest in its copper mines, which date from the Bronze Age.
However, no finds from before this period had been uncovered.
The "bann flake" knife was most likely used in the making of fish traps or in hunting by nomadic hunter-gatherers, Mr Gibbons said yesterday. It is currently being photographed and studied.
A bann flake knife is a kind of leaf-shaped stone flake found widely among the later Mesolithic artefacts from Northern Ireland and the Isle of Man. The name relates to the Bann culture.