Mponeng Gold Mine

Mponeng is a gold mine in South Africa's Gauteng province.  It extends over  below the surface, and is considered to be one of the most substantial gold mines in the world.  It is also currently the world's deepest mine from ground level.  The trip from the surface to the bottom of the mine takes over an hour. 

Over 5400 metric tonnes of rock are excavated from Mponeng each day.  At a price of $19.4 per gram of gold, the mine only needs to extract 10 grams of gold per ton excavated to remain profitable.  The mine contains at least two gold reefs, with the deepest one metre thick. 

Physical conditions
The temperature of the rock reaches , and the mine pumps slurry ice underground to cool the tunnel air to below .  A mixture of concrete, water, and rock is packed into excavated areas, which further acts as an insulator.  Tunnel walls are secured by flexible shotcrete reinforced with steel fibers, which is further held in place by diamond-mesh netting. 

In 2008, researchers looking for extremophile organisms discovered the bacterium Desulforudis audaxviator present within groundwater samples from kilometers deep in the mine. 

In popular culture
Danny Forster visited the mine for the fifth episode of Build It Bigger's eighth season. 

References

Category:Gold mines in South Africa
Category:Economy of Gauteng