Maybe, but I'm not sure that's a useful answer. Obviously, in general, a larger country has more resources than a smaller one.

The presence or absence of minerals is solely dependent on geology. As mentioned, SA has kimberlite pipes. Gold is commonly found in areas with large igneous instrusive bodies. SA has those.

Rather than size, age might be a better indicator. SA contains, or partly comprises, some very old rock. What that means is that many, many varied geologic processes have occurred in that region over the billions of years, as opposed to a younger terrane. Higher probability that processes that tend to concentrate gold will have taken place.