> I am not entirely sure why, but what's happening is that in most ceramics, a scratch creates a place where the stresses inside the material get amplified in a

> I am not entirely sure why, but what's happening is that in most ceramics, a scratch creates a place where the stresses inside the material get amplified in a way that doesn't exist with metals. So in metals those cracks also don't like to propagate much; it's really in glass where you see cracks propagate through the whole material. Covalent versus metallic bonds between atoms. You can model glass like a bunch of tiny spheres (atoms) joined by sticks (covalent bonds). You break a stick by moving two balls, it tends to stay broken most of the time. You can model metals like a bunch of tiny spheres (atoms) submerged in a glue-y fluid (cloud of shared electrons that makes the metallic bonds). You can move the balls around within that sticky cloud, to some extent. The comparison is very, very metaphorical, but it gives an idea why metals are more resilient to cracking.