Solid Energy's chairman says the company has grown and developed substantially under the leadership of chief executive Don Elder who has quit suddenly.
Don Elder announced his resignation on Monday after 12 years at the helm, saying his departure follows discussions underway for some time.
He has been an active proponent for the development of the coal industry, but was heavily criticised last year when Solid Energy mothballed mines and cut hundreds of jobs in response to sharp falls in the price of coal.
Dr Elder says it is the right time for a new chief executive to lead the restructured firm and remains available to assist with the transition.
Solid Energy chairman Mark Ford says the company has grown and developed substantially under his leadership.
Mark Cadzow, chairman of industry lobby group Straterra, says Dr Elder made some difficult decisions to ensure that Solid Energy continues to thrive.
He says Dr Elder has been a forward thinker and it would be a shame for him to be lost to the industry.
Former chairman John Palmer also praised Dr Elder for his work, saying he has a lot to be proud of during his time at Solid Energy.
He says Dr Elder was enormously hard working and always with the best interests of the company and his staff at heart.
Solid Energy senior executive Garry Diack will become acting chief executive until a permanent replacement is found.