A distant region that has one resource in such abundance that the limitation is on what you can spend it on because of limited transport.
In absolute terms, Mali had a lot of gold. Not quite "Bolivian silver" amounts of gold, but definitely the most easily recovered reserves of gold by pre-chemistry methods. If we measure strictly by the amount of gold that was held by any country all at once, then there probably was a point where Mali was the wealthiest country on the planet. But if you can't buy anything with it because you're on the wrong side of the desert, it doesn't really matter that you have bricks of shiny yellow metal.
Mali is a strange case.
A distant region that has one resource in such abundance that the limitation is on what you can spend it on because of limited transport.
In absolute terms, Mali had a lot of gold. Not quite "Bolivian silver" amounts of gold, but definitely the most easily recovered reserves of gold by pre-chemistry methods. If we measure strictly by the amount of gold that was held by any country all at once, then there probably was a point where Mali was the wealthiest country on the planet. But if you can't buy anything with it because you're on the wrong side of the desert, it doesn't really matter that you have bricks of shiny yellow metal.