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.

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.

Block 75
Block 75 is a block representing an off-state Redstone Torch. when a normal Redstone Torch receives power it turns off, turning to this block, and stop giving power. When the torch stops getting power it turns back to the normal on-state torch, and gives power again. For the game to know the torch stopped getting power the game must update the block - this happens when a block near the torch changes, and when it turned off because of Redstone current, this is not a problem, but when spawned into the world it will be turn off, and because no block is updated, it will stay this way, until a block updates. When the block is removed it will turn to a normal on-state torch.

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.

Farmland
Farmland is a block on which seeds can be planted and grown, and it is made by using a Hoe on Dirt or Grass. If Farmland is near water it becomes hydrated, and if not it turns dried again, and eventually back to Dirt.

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.

Block 97
Block 97 is a block that may look like a Stone block, a Cobblestone block, or a Stone Brick block, but is actually a block that when destroyed will spawn a Silverfish. The block is easily destroyed by hand, distinguishing it from regular blocks. If you attack a Silverfish directly with a sword or a bow, nearby Block 97 will break, spawning other aggressive Silverfish.

Nether Portal
Nether Portal blocks are generated when a portal is formed, standing on them will teleport The Player from The Overworld to the Nether and vice versa. However they become transparent when another "portal" block is placed next to it (the only way to do this is through inventory editing). When invisible they are still detectable and can still send you from the Overworld to the Nether and vice versa.

End Portal Frame
End Portal Frame is a block that can be found in strongholds, it has a decorative bluish-green top, while the sides and bottom are an off-white color, decorated in hollow rounded rectangles with the same color as the top. They are found in a 12 block ring shape within a room over a pool of lava and a staircase containing a Silverfish spawner.

Uses
Some of the blocks have an Eye of Ender inserted into it, Using other Eyes of Ender on the rest of the blocks inserts them to the top of the blocks. Once an Eye of Ender has been inserted in all 12 Frame blocks, then the Ender Portal will activate and the player can pass through to access The End.

History
The Ender Portal Frame used to have a different texture, emitted a blue shaded light at level 15 and was non-solid block when cracked, becoming solid when repaired. Although it couldn't be mined, an explosion caused them to drop as an item shaped like a Glass Pane. They had no tooltip, indicating that them dropping at all was a bug. The player had to repair a cracked Ender Portal Frame by right clicking it with an Eye of Ender.

End Portal
Ender Portal are unused that will teleport the player into The End dimension. It looks like a white-on-black two-dimensional star map, and emits light and black smoke particles. Only the top and the bottom sides of the block are visible, and the bottom side is invisible. In addition, the bottom cannot be passed through, although the sides and top can be. The collision box for this block takes up the lower 1/16th of the block, similar to Snow.

Trivia

 * Stepping into the portal is somewhat like a leap of faith, as the player must trust the portal will take them to The End instantly, before they fall into the lava pool beneath.