As far as I'm aware, the bombs don't "vaporize" blocks and only drops them as items (except walls that were generated at the start like dirt walls or ebonstone walls). I have often wondered if that bomb that I just threw would blow-up that worthless blowpipe that I didn't want to pick up but I wanted the chest it was in so I took it anyways. Long story short, I haven't blown-up a dropped item yet.

EDIT: I have obtained the Rocket Launcher and used it with Rocket IV's to blow massive holes in the world...the answer is still cannot vaporize items

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