what was the richest discovery in the history of mining?

Answer 1

The Comstock silver deposits of Virginia City, Nevada; South African diamonds at Kimberley, Zambian copper, Australian opals. In ancient times, the British Isles were famed for their silver and attracted traders from all over the known world.

The exact amount of most ancient deposits is unknown as nobody kept records.

In the modern world, minerals such as uranium and titanium are often more highly valued than siver and gold, in which case the uranium mines of Canada may rank high in value.

Answer 2

I'd go with the diamond deposits in South Africa. They supply something like 90% of the world's supply of diamonds. Although the recent discovery of diamonds in northern Canada has the potential to overtake them eventually.

Answer 3

There is no definitive answer to this. I'd say the silver mines of Bolivia might be the single most influential.