Employees at the Endako mines open pit drilling and milling operations in northern B.C. are now part of United Steelworkers (USW) Local 1-424.
As of Thursday, 260 workers were granted membership by the BC Labour Relations Board.
USW Local 1-424 is based in Prince George.
The mine, located 190 km west or Prince George, primarily produces molybdenum which is used in the fabrication of alloy metals, stainless steel, chemicals and lubricants and other products.
"Our union looks forward to working with the new membership at Endako mines," said USW Western Canada director Stephen Hunt. "We congratulate them for taking the step to unionize and we are confident that we can work together to negotiate a good, solid first agreement with this employer."
