there wasnt many irish back then due to the ice age. and the ones that were there survived off hunter gathering due to the plentiful wildlife that emerged from the glaciers lifting up and moving dirth around.
futhermore, when people did return to ireland post ice age they found rich copper ore deposits that the glaciers had made easy to extract.
what ended up happening is the irish turned these ores into useful tools and decorative things and traded them to other countries for whatever they needed.
in retrospect, im glad they got rid of their copper. as it was one less thing the british could have stolen from them