Metal ores to make the Olympic medals will come from mines in the USA and Mongolia belonging to mining firm Rio Tinto, London 2012 organisers said.
The company will provide metals for 4,700 gold, silver and bronze medals for the Olympic and Paralympic Games.
Rio Tinto said the metals will come from its Kennecott Utah Copper mine in Salt Lake City, USA, and the Oyu Tolgoi mine in Mongolia.
The firm supplied ore for medals at the 2002 Winter Games in Salt Lake City.
Modern gold Olympic medals are plated with about 6g of gold, while the runners up medals are struck from pure silver.
Chris Townsend, the commercial director for London Organising Committee of the Olympic Games and Paralympic Games, said: "The medals are one of the great traditions and enduring images of any Olympic or Paralympic Games, so Rio Tinto will play a significant role in the successful delivery of London 2012."
He said he hoped the medals will be "spectacular and sustainable."
Tom Albanese, chief executive of Rio Tinto, said the firm was "excited to have the special job once again of digging the ore that will become treasured medals for the world's elite athletes".
The Royal Mint was awarded the contract to produce athletes' medals for the Games and the design for the medals will be revealed in the summer.