His resignation comes at a time of unprecedented trouble in South Africa's platinum industry, where violent strikes for higher wages have left almost 50 people dead.
The chief executive of miner Aquarius Platinum, industry veteran Stuart Murray, has resigned with immediate effect after a decade at the helm, becoming the third boss of a major platinum producer to step down so far this year.
Aquarius, which announced the departure in a statement on Monday, gave no reason for Murray's resignation. But the move comes at a time of unprecedented trouble in South Africa's platinum industry, where strikes for higher wages have left almost 50 people dead, as the country experiences its worst social unrest since the end of apartheid in 1994.
Murray, a chemical engineer who began his career with number two player Impala Platinum, was well-known in the industry for his frank and sometimes controversial public comments, and his departure hit Aquarius shares, as investors fretted it could signal more bad news to come.
During his time at the helm, Murray oversaw the growth of the company from a single mine to number four player, and steered it through tough times. Those times included a mine accident in 2010 that killed five employees and Zimbabwean efforts to claim a larger slice of mining revenue via "indigenisation" policies that threatened its Mimosa venture.
More recently, along with other executives in the sector, he battled low platinum prices, safety stoppages and squeezed margins that dragged Aquarius to a full-year loss.
Aquarius, which gets most of its production from South Africa but also has the Mimosa mine in Zimbabwe, was one of the first major platinum miners to scale back activities because of low prices, suspending operations at its Marikana joint venture with Anglo American Platinum in June.
"Stuart Murray has pretty much been the face of Aquarius Platinum," Nomura analysts said in a morning note.
"After an extremely difficult last three years for the company there will be plenty of speculation surrounding whether or not there is more bad news to come."
News of the resignation sent London-listed shares in Aquarius down 10.5 percent to 42.99 pence at 0900 GMT, underperforming a 1.2 percent drop in the broader UK mining sector. Australian-listed shares closed down 6 percent, while its Johannesburg stock fell almost 8 percent.
But Nomura analysts also saw positives, including a potential "fresh start" with new leadership for a miner that has evolved since Murray took the chief executive role in 2001.
A replacement for Murray - also chairman of the miner's principal, South African subsidiary - will be considered "in due course", Aquarius said, adding that he will continue at the miner until the end of March, for an "orderly handover".
Murray is the latest platinum boss to leave this year.
David Brown left the helm of Impala Platinum at the end of June, to be replaced by former Metorex boss Terence Goodlace, while Anglo American Platinum (Amplats) replaced veteran Neville Nicolau with iron ore executive Chris Griffith in July.
The third-largest platinum producer, Lonmin, has appointed an acting chief executive as boss Ian Farmer pursues treatment for an unspecified illness.
Aquarius, which in August reported a full-year loss for the 12 months ended June 30, said that Jean Nel, formerly commercial director, would become its chief operating officer.
Zwelakhe Mankazana, a non-executive board member since 2007, has been appointed interim non-executive chairman of Aquarius' principal subsidiary, Aquarius Platinum South Africa.