Mining giant Anglo American announced on Wednesday the sale of three platinum mines in South Africa to Sibanye Gold, the country's biggest producer of gold, for 4.5 billion rand ($332 million).

The two companies opened talks last week as the platinum industry struggles with falling prices and industrial unrest.

"We are pleased to announce a significant milestone in the repositioning of our portfolio with the disposal of the Rustenburg Operations to Sibanye," Anglo American Platinum CEO Chris Griffith said in a statement.

The company said the sale was part of a move towards low-cost operations, as it removes loss-making elements from its portfolio.

Prices for platinum, which is mainly used in jewellery and catalytic converters for vehicles, have dropped by about 40 percent since 2011, and are at their lowest in six years.

Sibanye will pay 1.5 billion rand upfront, paying the remainder over the next six years from the cash flow of the newly-acquired mines.

South African mining has been hit by China's economic slowdown, which spooked stock markets worldwide in recent weeks and sparked a rout in emerging market currencies.

London-based Anglo American and rival Lonmin have both announced plans to reduce their workforce in South Africa, with trade unions warning 19,000 job cuts could be lost across the mining sector.

South Africa, which produces 70 percent of the world's platinum, was badly hit by a five-month strike by 70,000 platinum miners in 2014.