Synthetic diamonds had no effect because diamonds themselves aren't rare in anyway shape or form. They're used in sandpaper, as mentioned the monopoly of their supply is why the vast majority hold value.
I have a .5mm mechanical pencil it's a uni-ball with lead that is Diamond infused I wonder if those are real diamonds?
The writing "lead" is graphite ( carbon ) with binder material to provide a framework, and formed into a thin rod under pressure and heat. Diamonds are carbon after extreme pressure and heat. So yes, they are probably "diamonds" of nano size in the material. I doubt naturally, as they say infused, so most likely synthetic material added in the process. Actually, friends say it is the best pencil lead.
Yeah, since they banned it, there's only one real way to put real lead in your pencil these days... Snake Venom Beer. 67.5 ABV (Yeah, you read that right, 135 proof beer!) That'll put lead in your pencil!
Meh. I've got real barleywines, and a bottle of Everclear, so I'm ahead of the game. Besides, didn't they stop making this?