Although China is poised to overtake the U.S. as the second-biggest gold producer this year - and perhaps South Africa as the largest - Zijin Mining Group Co. says existing mines will run out of ore in six years.

Rising economic growth in China has led Zijin Mining, Zhongjin Gold Corp. and other Chinese producers to increase production. Existing mines are now approaching the end of their mineability terms.

The U.S. produced about 260 tonnes last year with China just 20 tonnes behind at 240 tonnes. South Africa was at 275 tonnes, but could substantially drop this year due to strikes and mining accidents.