Cerro Rico is a crazy place, geologically speaking. Apparently around 800 million ounces of silver (22,695 metric tons) were produced between 1545 and 1823 [1], and even after about half a millennium of mining it still has another 1.7 billion ounces in estimated silver reserves [2].
It's a swiss cheese of tunnels by now, so much so that the summit is subsiding at a rate of a few cm/yr [2] due to the gradual collapse of the mountain.