Solid Energy chief executive Don Elder says it does not make economic sense to keep its Spring Creek coal mine open - though no decision on its future has been made.
This week, the state-owned miner announced job cuts at its East Huntly coal mine and head office and is suspending operations at the Spring Creek mine on the West Coast.
Dr Elder says the company has spent $125 million on the mine since it opened more than a decade ago, including $90 million over the past year.
He says if it stays open, it would need another $70 million over the coming year, and even then the business would not be viable due to current international coal prices.
"That would be an irrational business decision, on the face of the economics, but we're still working through that before we get to the final answer.
"It's a very difficult decision given that there are 230 jobs at stake here."
Dr Elder said mothballing the mine also costs money.