Staff have been through an upskilling and induction process.
Tara Mines is fully operational again after an 18-month lay off.
Owner of the mines, Boliden, closed the facility last year, with a temporarily loss of over 600 jobs.
200 workers have taken a voluntary redundancy package, meaning the 405 remaining needed to upskill, with many just completing a return to work induction training and familiarisation process.
SIPTU Sector Organiser, John Regan, says: “There is a sense of relief among workers and the communities throughout the north-east with the full reopening of the mine and the first blast to develop a mineral vein, taking place this week."
While SIPTU Organiser, Andrew McGuinness says the reduction in labour costs and a change in mineral prices should see the mines return to profit in the short term.
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