Titanstone Block

Bombs and dynamite bounce off it, which is the one property that makes it worth crafting rather than just a recolor. Line the walls of a bomb-mining shaft with it and you can blast freely without opening a hole into your own tunnel. In a shared world it also stops a careless dynamite throw from redecorating someone's build.

One piece of ore now stretches into a run of blocks rather than converting one for one, so covering a large structure in it does not eat the ore you wanted for gear. Which of the two hardmode bricks your world offers is decided at generation, and the Adamantite Beam is the other face of the same idea.