Technical blocks

Technical blocks are blocks that cannot be acquired legitimately and serve various purposes during events within the game.

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

Piston Extension
Block 34 is a block used by the piston's extension arm. One of the data bits of this block defines if it is a normal piston or a sticky piston extension.

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. When a block next to it is removed, it becomes invisible, can be walked through, and when light passes through it the light level decreases by 1. They are unbreakable by traditional methods; 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, and it cannot be placed.

A group of these blocks are also known as or nicknamed 'the shadow glitch' and as of 1.8, can appear on objects such as beds, signs, chests, paintings and other placed items. It is common to see paintings affected by block 36, and if unwanted the player can simply mine the block above the picture to remove.

Burning Furnace
This is a block used to make furnaces shed light when smelting. It has a different texture than the normal furnace and emits particles. If the burning furnace is activated and the fuel runs out, the block will return to a normal Furnace.

Glowing Redstone Ore
This is a block used to make Redstone Ore glow when stepped on, right-clicked, or left-clicked.

Off-state Redstone Torch
This is like a Redstone Torch, but it's off when it's first placed. Destroying this will give an On-state Redstone Torch. If placed, will turn on when an adjacent block changes.

Active Redstone Repeater
This is the on state of the Redstone Repeater.

Flowing Water
The flowing water block tells the game to check for any air blocks around it and put some water into them if applicable.

Flowing Lava
The flowing lava block tells the game to check for any air blocks around it and put some lava into them if applicable.

Pumpkin Stem
The block that is planted on farmland when pumpkin seeds are used on it. It starts off-set under-ground, and rises up as the plant grows, as opposed to the method wheat seeds uses, where each growth stage is an individual texture. The stem is coloured green by the game, and then brown once fully grown.

The stem will change to the second image once a pumpkin has grown off the stem. A single stem will connect to any Pumpkin in an adjacent square, thus there are 5 possible appearances to a stem. When the pumpkin is removed, the stem will return to its original image.

A single pumpkin will grow off a full grown stem at a time, but once that pumpkin is removed, another can grow in its place.

Destroying a fully-grown stem yields 0-3 pumpkin seeds.

Melon Stem
The block that is planted on farmland when melon seeds are used on it. The colouring and growth method is the same as the Pumpkin Stem's.

The stem will change to the second image once a melon has grown off the stem. A single stem will connect to any Melon in an adjacent square, thus there are 4 possible appearances to a stem with a melon on it and 1 without. When the melon is removed, the stem will return to its original image.

A single melon will grow off a full grown stem at a time, but once that melon is removed, another can grow in its place.

Destroying a fully-grown stem yields 0-3 melon seeds.

Silverfish Block
A Silverfish will hide inside a Stone, Cobblestone, or Stone Brick block, changing it into a Hidden Silverfish block. The block is easily destroyed by hand, distinguishing it from regular blocks.