There is a question that's bugged me for years...and I'm not the only one, it seems:
It's canon that anything that comes from Krypton is indestructible in our environment--cloth, glass, whatever.
But Earth criminals seem to have no problem taking Kryptonite and fashioning it into whatever size & shape they need--rings, bullets, knives, paint, doorknobs, whatever...shouldn't actual chunks of Krypton be at least as indestructible as thread from Krypton?
Well, of course, there's an answer:
Of course, if it was so unlikely that any Kryptonite which hadn't passed through the clouds could reach Earth, you have to wonder how Kal-El's rocket managed to make it to Earth without passing through one of them and "removing" the indestructibility of the rocket's glass windows, blankets, etc.
Also, it's too cute by half to insist that even though the Kryptonite was rendered not indestructible, it still somehow magic remains "friction-proof" (a necessary fiction or else most of the Kryptonite meteors would disintegrate whilst plummeting through Earth's atmosphere).
Not indestructible, but friction-proof.
From Superboy #134 (1966)