JOHANNESBURG'S gold mining industry was established when a large gold reef was accidentally discovered on a remote farm in 1886, triggering a massive gold rush by thousands of speculators. Within 10 years, there was a fully fledged town on the same spot; within 30 years it was South Africa's largest city. Today Johannesburg is Africa's biggest city, ringed by the deepest gold mines in the world.

The major gold and diamond mining houses all have their headquarters in Johannesburg, the biggest being Anglo American and De Beers.

There are 159 mines - 44 of them gold mines - in Gauteng that together produce a quarter of South Africa's total mineral production. Most of the mining is for gold - 80% of Gauteng's output.

Although gold mining and ancillary industries provide thousands of jobs, mining is increasingly less important to the city than the manufacturing and financial sectors. Mining produces only 6% of Gauteng's total income and 31% of export earnings.