International Coal CEO Glenn Simpson has quit the miner.
Simpson stated that he will resign "due to health reasons".
He will continue with the company until 6 June, during which time he will help the company during the transition period.
International Coal will now start a search for a new chief executive, with executive director Hugh Dai to act as interim CEO until a new successor is appointed.
The miner has a number of tenements in Queensland's Bowen and Surat Basins.