Diamonds have a cleavage, similar to the grain of wood, and can split, crack or splinter along those cleaves.
How is it possible that diamonds can't be scratched but can be broken? Isn't a scratch simply the beginning of a breakage?
Hardness can also be brittle the hardest knives will break a cheap softer one will bend
Most diamonds have tiny flaws and that's where they are prone to breakage.
Diamonds can be burned too. It just needs a very hot fire and lots of oxygen 💍
A diamond can be scratched by another diamond.