Brimstone

Brimstone is a dark-colored block that functions similarly to cobblestone. It can be found only in the Nether.

World generation
Brimstone can be found in the Nether in large veins.

Breaking
Brimstone can be mined with any kind of pickaxe.

Crafting
Brimstone can be used in place of cobblestone in some crafting recipes that use it.