The CEO of mining company Lonmin, Ian Farmer, has stepped down from his position, the company said on Friday.
"Farmer, who is being treated for a serious illness, has informed the board of his request to step down as chief executive officer...and as a director," Lonmin said in a statement.
He leaves the company with immediate effect.
Lonmin Chairman, Roger Phillimore, said Farmer would be greatly missed.
"He has been CEO for the last four years and the consistent improvement in Lonmin's operating performance over that period owes much to his leadership."
The company has now appointed an agent to find a successor to Farmer.
Simon Scott, continues as acting CEO but has asked not to be considered for permanent employment in the position.
Scott will return to his role as chief financial officer, once a replacement for Farmer is found.
Lonmin made national and international headlines when police shot dead 34 mineworkers on August 16 after they clashed during a wildcat strike at the platinum mine in Marikana.
A commission of inquiry into the matter has since begun unravelling the events behind this tragedy.