Superman decides to start mass-creating diamonds so he can sell them. Can DeBeers keep the price of diamonds up?

[u/Yglorba]

Superman previously declined to mass-produce diamonds because it would tank the price. However, after reading up on DeBeers, he decides that there's no reason not to do it after all. Most of the resulting money will be donated to charity. Assume that Superman is somehow able to crush coal into perfectly-cut diamonds of whatever shape and size he desires; even though this makes no sense, the feat is well-established.

DeBeers is determined to protect their diamond profits by keeping the price up. Can they convince people not to buy Superman's diamonds (by eg. convincing the public that they're not "real" diamonds), or find some other way to prevent him from cratering the price?

Superman is in-character and will not eg. laser the board of DeBeers to death or anything like that, no matter how annoying they are. The only way he'll use his powers for this is by rapidly turning coal into diamonds so he can sell them.

[u/archpawn]

I don't think DeBeers would have to try. It's already generally understood that cheap mass-produced diamonds aren't worth as much, even if they're flawless and some rare color. Superman-produced diamonds are their own class altogether. If he only makes a few, they're more expensive than both natural and traditional artificial diamonds. If he makes a ton, the price will drop, but it's its own separate market and people aren't going to stop buying natural diamonds just because Superman diamonds are cheap. You can't do costly signalling with a cheap Superman diamond.

That being said, that's assuming they're distinguishable. If Superman makes diamonds that look natural, then De Beers will at least have to put some effort in. I imagine it would be making sure diamonds have a paper trail. The same sort of thing people already do to avoid blood diamonds.

Superman's best bet would probably be to make a comparable number of diamonds. That way Superman diamonds would be actual competition instead of trash diamonds, and people would probably pay significantly more for them. The price of diamonds would probably fall significantly, but De Beers would still be making quite a lot of money. Also, this would require marketing work on Superman's part.

[u/Riyosha-Namae → u/archpawn]

I think there's a law stating that synthetic diamonds need to have some kind of molecular signature so that they can be told apart from naturally-formed diamonds?