Somehow I don’t think Errol Musk knew that much about the geology. Allegedly he bought the shares on a whim without first visiting the mine, which was in a different country.

Mines can absolutely become suddenly unprofitable. You don’t know how much good stuff is in the ground until you dig it up.

The mine went bankrupt in '89, just a few years after Errol bought shares in it. The boss was someone else.