SIPTU is neither “optimistic or pessimistic” ahead of a meeting today at the Workplace Relations Commission about the Tara Mines.
Last month, hundreds of employees were temporarily laid off, with its owner, Boliden Group, blaming rising bills and a collapse in the price of zinc.
"The Tara zinc mine in Ireland is a high-cost mine with approximately 650 employees," the company said at the time.
"Boliden is working actively to extend the life of the mine in parallel with ensuring its competitiveness.
"The business is currently cash flow negative, due to a combination of factors including operational challenges, a decline in the price of zinc, high energy prices and general cost inflation.
"Tara will therefore be placed under care and maintenance until further notice.”
Boliden has warned that a protest by workers which began on Wednesday evening could jepordise chance of a deal and SIPTU Division Organiser Adrian Kane was unwilling to speculate about one.
“Well, I think it’s important that both sides continue to talk,” he said.
“I mean, I think it’d be fair to say that I’d neither be optimistic or pessimistic - but at least we’re engaging.
“We’ve always said we’ll meet the company any time, anywhere and so we’re meeting this morning with the WRC.”
Before it ceased operating, Tara was the largest zinc mine in Europe and the eighth-largest in the world.
Since extraction began in 1977, more than 85 million tonnes of ore have been mined.