How do you grind a diamond to dust?

Diamonds are made of carbon, with a very rigid and strong atomic structure. In order to grind a diamond into dust, you would need to use a material harder than diamond itself. The only known natural material harder than diamond is another diamond. Therefore, you would need to use a diamond saw to cut the original diamond into smaller pieces, and then use those smaller pieces to grind the original diamond into dust. This is a very difficult and time-consuming process, which is why diamond dust is so expensive.