I think that we need though blocks that stop explosions and such, and also be decorative. Smooth obsidian would fulfill this need, and also to come with slab and stairs variants (so we can have pretty decoration and blast resistance). Even a chiseled variant for the full size block could be an option. I made a mockup to show how could it look, compared to chiseled sandstone and red sandstone; there's the original version and a modified one to match better the sandstone's.
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