Ambrose Patrick McMullen (60s), originally from Cootehill, Co Cavan, died in the underground explosion at the Endeavor mine in Cobar, New South Wales.
Two women, both in their 20s, were brought to the surface, but one later died.
The second woman was airlifted to hospital for minor injuries and shock.
The mine is about 700km northwest of Sydney.
Police said emergency services were called to the scene at approximately 3.45am after receiving reports of two people critically injured in a workplace incident. Officers said a man in his 60s had been confirmed dead.
Police said all three workers lived in Cobar.
Mr McMullen had left Cootehill in the mid-80s to travel and later settled in Australia, where he has lived with his family since.
Local councillor for Bailieborough and Cootehill, Carmel Brady, said Mr McMullen was her classmate in school. She said he found a “new home and life down under in Australia”.
“I was in the same year at secondary school, St Aidan’s Comprehensive School, as Ambie.
“He was a kind, friendly young man who excelled at all sports.
“Very sad news was felt in the town of Cootehill last night when word broke.”
Mr McMullen was from a well-known family in the area, Ms Brady said.
He is survived by his sister Mary and brother Kevin, who still live in the area, and a younger sister, Dympna.
“I wish to extend my deepest sympathy to his immediate family in Australia and his family here in Cootehill. Rest in peace, Ambie,” Ms Brady added.
Australian police (Getty Images)
Today’s News in 90 Seconds – Tuesday, October 28
In a tribute, Cootehill Chamber described Mr McMullen as “well-known and fondly remembered in our community”.
“We extend our deepest sympathies to the family, friends, and loved ones of Ambrose ‘Ambie’ McMullen, Cootehill, who tragically lost his life in a mining explosion in Australia,” a spokesperson wrote in a post on Facebook.
“Ambie was well known and fondly remembered in our community, and his untimely passing has deeply saddened all who knew him. Our thoughts and prayers are with his family at this heartbreaking time,” they added.
A spokesperson for the Department of Foreign Affairs told the Irish Independent the Department is “aware of reports” and “stands ready to provide consular assistance”.
“The Department does not comment on individual cases,” a spokesperson added.
Fatalities from mine explosions are rare in Australia, with the most recent death happening in 2015 at a mine in Queensland.
Cobar Mayor Jarrod Marsden said it was an “absolutely tragic” situation.
“The most valuable thing to come out of a mine are the miners, and two families don’t get to see their loved ones anymore,” he told the Australian Broadcasting Corporation (ABC).
“Cobar is a small mining community, it’s very tight-knit, and I’m sure everyone’s going to be thinking of their families today.”
NSW Premier Chris Minns extended his condolences to the family, friends and colleagues of the workers who died.
“This is a heartbreaking day for the Cobar community and will be felt across the entire mining industry,” he said.
Safety protocols and procedures have “greatly improved in mining”, Minns said, but the two deaths were a “sobering reminder of why we need to always remain vigilant to protect workers”.