The world's largest gold deposit is the Witwatersrand gold deposit, referred to as the RAND gold deposit. It was discovered in 1866, soon put into production, has been more than 140 years. The South African capital, Johannesburg, was founded on the gold rush.
So far, the RAND gold mine has produced 35 thousand tons of gold, there are reserves of 18 thousand tons, accounting for 52% of the world's total gold reserves of gold. The mine's 1970 annual output of gold reached 1000 tons, the highest annual output for the history. Since then, the mine has maintained an annual output of 700 to 650 tons of gold, accounting for half of the world's gold production. The ore reserves and output ranking first in the world, is the world's largest gold mine. High gold grade of the mine is also rare in the world, is still maintained at 7 to 20 grams / ton, an average of 10 grams / ton.
400 km north and south of the basin. Gold bearing gravel strata located in the surrounding area of the basin, with a total length of 480 km gold belt, ore area of 20 thousand and 700 square kilometers, the largest of a main ore belt length of 190 km. Ore bearing layer is thicker than 100 meters, there are 200 layers of ore bearing strata, the main ore layer 10, 0.15 - 1.14 meters thick. At present, the mining depth has reached 3600 meters, gold change is not relatively stable, but due to the mining depth increased, equipment aging, grade also has reduced, and thus the cost increased, the cost per ounce to reach 400 - 350.