Amplats, a unit of global mining giant Anglo American, said Griffith's successor was expected to be an internal candidate and would be announced soon.

"After more than seven years at the helm, and given all that we as a team have achieved, this is now the natural time for the next generation of leadership to take this business forward and deliver further value," Griffith said.

Shares in Amplats were up 4% at 1,311.97 rand by 1222 GMT.

Fifty-five year old Griffith, who has a background in mining engineering, said he did not yet have plans for what he would do next and would not rule out a career outside mining.

Appointed CEO in September 2012, Griffith headed Amplats during its turnaround plan to cut production and costs in response to platinum prices, which then were depressed.

South Africa is the world's leading miner of the metal used in catalytic converters, medical equipment and jewellery.

The sector has suffered from industry unrest, including a five-month strike in 2014 followed by deep job cuts, as well as volatile demand.

"Over the course of a few years, having to retrench 20,000 people was I think the worst time in my career," Griffith said.

Griffith's first job was at Amplat's Amandelbult in Limpopo, where he helped to move ore and waste rock in the underground operations during his university holidays. He rose through the ranks to become the youngest mine general manager in the company's history in his early 30s.

PALLADIUM AND RHODIUM BOOST PROFITS

The South Africa-based miner, which also has operations in Zimbabwe, said higher metal prices had driven its annual headline earnings per share - the main profit measure used in South Africa - nearly 2-1/2 times higher at 70.87 rand, versus 28.93 rand a year earlier.

Palladium and rhodium prices, widely used in vehicle exhausts to reduce harmful emissions, have climbed as tighter environmental regulations force carmakers to buy more of the precious metal used in catalytic converters.

The price rise has boosted profits at miners such as Amplats, Sibanye-Stillwater, and Impala Platinum after several years of losses.

Earnings before interest, tax, depreciation and amortisation (EBITDA) doubled to 30 billion rand ($2.02 billion) from the year-ago period.

Amplats declared a final dividend of 41.60 rand per share, made up of 16.60 rand base dividend and 25.00 rand special dividend, bringing the gross dividend, the highest since 2006, to 52.60 rand per share compared with 11.25 rand on-year.

Platinum group metal (PGM) production rose 1% to 4.4 million ounces.

($1 = 14.8602 rand)

(Reporting by Tanisha Heiberg; Editing by Tom Hogue, Sherry Jacob-Phillips and Barbara Lewis)

By Tanisha Heiberg