Technical blocks

Technical blocks are blocks that cannot be achieved legitimately and serve a purpose during events within the game.

Piston related technical blocks
These blocks serve a purpose when a piston is used.

Piston Head
Block 34 is a block used by the piston's extension arm.

Block 36
Block 36 is a block used by pistons, it is a side effect of the method of storing moving blocks as tile entities instead of entities. This block's color, when located next to a block in the world, is black, but when a block next to it is removed it becomes invisible, it can be walked through, and when light passes through it it decreases the light level by 1. They are unbreakable in traditional ways; however, can be removed by right-clicking. The game treats the block as stone when it comes to breaking animation and step sound. In the inventory it has a top of grass block texture in terrain.png, presumably since it is the first texture from it, and it cannot be placed.

Burning Furnace
A block used to make furnaces illuminate light when smelting, it also has a different texture then the normal furnace, and also emits particles.

Glowing Redstone Ore
A block used to make Redstone Ores glow when stepped on, right-clicked, or left-clicked.

Off-state Redstone Torch
Like a Redstone Torch, but it's off when placed. Destroying this will give an On-state Redstone Torch. Also, if placed, will turn on when an adjacent block changes.