We need some sort of nonflammable black building block!

This has been a much-requested feature, and a lot of people have put their ideas out there. I have seen black/dark quartz, basalt, black/dark granite, polished obsidian, and more. I like all of these ideas, and I have my own to put forth as well. I think that black/dark quartz should be just like normal, but the ore in the nether should be only found at and below level 31. This is the layer at which the lava oceans are, forcing players to mine. Basalt is also a cool idea, and I think that the consensus is that it can either be a new nether block, or an overworld stone variant. Black/dark granite is also pretty interesting as a concept, and I think the recipe should be 8 granite around 1 obsidian, giving 9 black/dark granite. Polished obsidian is a fairly popular suggestion with a self-explanatory recipe, the same as stone variants. These are good ideas! But we still need to find one or two that we think are the best. Other ideas are welcomed! So what do you think? What should our nonflammable black building block be?