Block of Redstone

Blocks of Redstone are mineral blocks and act as piston-movable redstone power sources which cannot be turned off. When power is applied to the block, it is unaffected and will still output a redstone pulse regardless. However, because of the way blocks act, it cannot power blocks adjacent to it.

Usage
The block of redstone was introduced mainly to serve the purpose of providing a solid block that can act as a redstone source.

A block of redstone will power adjacent redstone wire (including above and below), correctly-facing redstone repeaters and redstone comparators, and adjacent mechanisms (pistons, redstone lamps, etc.). It will not power adjacent opaque blocks. Redstone wire will configure itself to point towards an adjacent block of redstone.

The block of redstone also serves as compact storage for redstone, like other blocks of minerals (block of iron, block of gold, etc.).

Another usage of the block is to create a movable power source. The block of redstone can be pushed by a piston, and can generally make circuits involving pistons more compact.

Yet another use for this block is to re-strengthen redstone circuits. This works by using a Sticky Piston connected to a block of redstone in a way that when the circuit is powered, the piston activates and pushes the block of redstone so that the rest of the circuit is powered. However, a redstone repeater can do this job in only 1 block of space, albeit with a 1-tick delay.

Trivia

 * Blocks of redstone can absorb explosions. If an explosion (TNT, Creeper, etc) occurs on one side of a wall of redstone blocks, the redstone blocks will fall to the ground, but any blocks on the opposite side will remain unaffected, including other TNT blocks.
 * Dinnerbone joked for April Fools 2013 about Redstone Blocks being able to craft Redstone Block Blocks, which are redstone blocks made out of redstone blocks.

Gallery
Redstone (Block) Bloque de redstone Redstone (bloc) 红石块 Красный камень (блок)