The short answer? Fine Bone china is from the sturdiest porcelain available. Hard to believe isn't it? But it's the truth nonetheless.
The myth persists that fine china is easily broken and very fragile. This is one of the reasons people refrain from using their good china more often. Why take the risk of it breaking? Indeed, why even buy such fragile china sets in the first place?
But a myth it is. Bone china is extremely chip resistant and will not break easily at all. Why? Because of the materials bone china is made up (animal bone ash among other things), the extreme heat under which it is fired (ranging up to almost 3,000 degrees), along with the glaze which functions as a glass barrier, fine china patterns such as Lenox Versailles and Royal Crown Derby Derby Border can be expected to last quite a long time, even with more consistent use. Supposedly, some people at a Canadian store even balanced a Lola racing car on four Wedgwood teacups!
It's ironic that people looking to avoid china that may break go with cheaper versions of porcelain that are even more likelier to break then bone china. This doesn't mean that bone china is unbreakable, it is not, no porcelain is even Corelle. But it does offer some thought to reconsider not using what you like and what is beautiful for fear of damaging it.