What type of minerals were mined at Johannesburg?

Johannesburg is renowned for its rich deposits of gold. The city is situated on the Witwatersrand, a prominent gold-bearing ridge in South Africa. Since its establishment in the late 1800s, Johannesburg has been a significant center for gold mining and is often referred to as the "City of Gold." The presence of gold in this region fueled the development of Johannesburg into one of the largest and most economically important cities in South Africa.