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Crushing and handsorting of copper ore, Ross Island After extraction, the copper ore was sorted outside the Bronze Age mine to remove as much of the barren limestone as possible. The mineralised fragments were then taken to work camps adjacent to the mines. The ore was then finely crushed using stone hammers, anvils and grinding stones, and continuously hand-sorted to provide a rich concentrate. The proximity of the lake shore raises the possibility of water separation, by washing the crushed ore to separate the heavier metallic content. Archaeological excavation of the early mine camp at Ross Island uncovered important evidence for the conversion of this mineralised rock to metal through the process of smelting. This involved burning the finely broken copper ore in a charcoal-fired pit furnace, to produce droplets of copper metal. These droplets were then re-melted to form small ingots, an example of which was found in a bog at Knockasarnet near Killarney. These pits represent the first copper smelting furnaces discovered from the Bronze Age in Ireland. Research has shown that the copper ore smelted here is naturally rich in arsenic, some of which passed into the resulting metal.
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