Hunter Valley mines were affected when truck drivers and explosives handlers went on strike for four hours on Tuesday, in protest against what they say is a proposed cut in their wages and conditions.
Transport Workers' Union NSW secretary-elect, Michael Aird, said Orica Explosives had refused to offer 130 truck drivers a fair enterprise agreement.
"TWU members have been left with no option but to take industrial action, which has seriously affected mines across the Hunter Valley owned by Rio Tinto and others," Mr Aird said.
"Our members are employed as truck drivers, delivering explosives to mine sites, and also as shot firers, who detonate the explosives, so without them on the job there is no blasting and nothing to mine.
"For more than 12 months our member-led team has been negotiating for a new enterprise agreement with Orica management. At every step of the way we have told the company we need an agreement that recognises our hard work and allows us to safely provide for our families".
Mr Aird said Orica management had refused to put a reasonable offer on the table. He said the company had offered a salary increase that was below inflation and rejected by 90 per cent of the workers.
He said industrial action had been necessary, and would continue, until Orica treated workers fairly.
Orica truck driver and TWU delegate, Scott Leighton, said workers were seeking a fair agreement, but management had refused to listen.
"We're not asking for the world; we just want an agreement that protects our jobs, allows us to provide for our families and to come home safely at night," Mr Leighton said.
Orica is a major provider of commercial explosives to mining companies.
A spokeswoman for Orica said the company was disappointed that members of the TWU in the Hunter Valley have not accepted its enterprise agreement offer in the most recent ballot.
"Orica is committed to continuing discussions with its employees with the aim of finalising an agreement," she said."The company is working closely with its customers to avoid operational disruption."