The CEO of global platinum miner Lonmin, Ian Farmer, is stepping down permanently due to 'serious illness'.
Farmer has been off work since August last year due to illness, and officially announced his resignation.
The company has not explained the nature of Farmer's illness.
"Lonmin plc announces that Ian Farmer, who is being treated for a serious illness, has informed the board of his request to step down as chief executive officer (CEO) and as a director of Lonmin with immediate effect," the company said.
"The board has appointed an executive search agent to pursue the selection and engagement of Ian's successor as CEO. In the meantime, Simon Scott will continue in his role as acting CEO with the full support of the Lonmin board.
"Simon has requested that he should not be considered as a candidate for the role of CEO. Following the appointment of a new CEO, Simon will dedicate his time fully to his role as chief financial officer."
Roger Phillimore, the chairman of Lonmin, said he will be missed at the company where he worked for the last 26 years, four of which were spent as the CEO.
"We wish him well with his ongoing treatment and will stay in close touch with him as a valued colleague and friend," Phillimore said.
It comes as the miner, along with a number of other South African miners, faced a difficult 2012, as violent strikes crippled the miners and left many dead.
Lonmin's operations are located in the Bushveld Complex in South Africa, where it operates the Marikana mine, and where nearly 80% of the worlds PGM resources are found.
Lonmin has a market cap of US$ 1.67 billion.