Don't underestimate the size of this country. We spent three weeks last year just pootling in Western Cape and one half of Eastern Cape. That agenda makes one decent holiday, and there's scarcily any Big Game around those parts.
The best scenic high land is around Kwazulu-Natal, with the battle sites and the coast around Durban. That;s another holiday.
Not sure about gold and diamonds - just big holes in the ground, surely, around Kimberley - miles from anywhere else and not particularly interesting scenary either?