But it doesn't matter where it comes from. What really matters about a diamond is its 4C standard.
The so-called 4C: refers to the four standards of carat, color, clarity and cut.
In the global diamond mines, most of the rough diamond mining is controlled by De Beers. Diamond cutting is done in Antwerp, Tel Aviv, new york and Mumbai.
Many merchants do not participate in the mining of rough diamonds at all, and even are "offline buyers" with De Beers.
So most of them don't even know the origin of the original diamond, and there is no basis to say that the diamonds they sell are South African diamonds.
As for why South African diamonds are popular, it is because the most famous "Cullinan" in South Africa, coupled with the touting of domestic merchants, has caused consumers to "not buy non-South African diamonds" today.
Finally, I would like to sum up a sentence for you: diamonds from world-renowned jewelers such as Cartier, Harry Winston and Tiffany, as well as ordinary jewelry stores selling diamonds on the roadside, all come from various producing areas around the world.
I hope my answer is helpful to you. You can keep asking questions.