What will happen to the economies of South Africa, Botswana, and many other sub-Saharan countries if the market for mined diamonds and other jewels collapses?
For South Africa the impact will be very small. The entire mining sector has shrunk to just 7% of the economy, with diamond mining being a tiny fraction of that. Botswana is far more at risk, as around a third of their government revenues come from either diamond sales or diamond mining-related activities. They're already trying to diversify their economy though, as diamond prices have been falling for some time now.