Nether Bricks

"Nether brick blocks came to Minecraft in version 1.0.0 – the first official release of the game. They generate naturally in only one place – the walls and pillars of nether fortresses, where they provide protection for those inside from ghast fireballs and other dangers. Unfortunately, there's usually more danger inside the fortresses than out, as they act as spawning grounds for blazes, wither skeletons and other terrors."

- Duncan Geere

Nether bricks are blocks used to form fortresses in the Nether.

Red nether bricks are decorative variants that do not naturally generate.

Obtaining
Nether bricks can be mined using any pickaxe. If mined without a pickaxe, it will drop nothing.

Natural generation
Nether bricks form the walls and supporting pillars of all fortresses.

Usage
Nether bricks are non-flammable and immune to ghast fireballs, making it a suitable shelter material for the Nether. When walking on it, it makes the same step sound as stone.

If a nether bricks block is inside the whole bounding box of a fortress (not just inside the individual parts), fortress mobs (such as blazes and wither skeletons) can spawn on it if other normal conditions are met.