Explanation:

- South Africa is well-known for its mineral wealth.

- Option 1, Copper: South Africa has some copper deposits but is not the leading exporter.

- Option 2, Diamond: South Africa has a rich history with diamonds but isn't the largest exporter in the current market.

- Option 3, Silver: South Africa does produce silver, but in smaller quantities compared to other minerals.

- Option 4, Gold: Historically, South Africa was a leading producer of gold. While production has decreased over the years, it still plays a significant role in the gold market.

Given the options, Gold (Option 4) is indeed a historically significant mineral from South Africa.