Diamonds are actually breakable, and not all that hard to break, if you hit them along the right axis. Diamond cutters use chisels, and that's enough to split a diamond.

I think you’re thinking of “unscratchable”. Diamonds are extremely hard and nearly impossible to scratch. But hardness is usually a trade off with elasticity, so they are also very brittle and therefore pretty “easy” to break.

Only if you buy them from the same place as your anime blu-rays.