Glowstone

Glowstone (formerly known as Lightstone) is a golden block that glows indefinitely. This block can only be found naturally in The Nether. It generates on the undersides of Netherrack, and forms unusual coral-like stalactites. Glowstone has a luminance of 15.

Glowstone can be difficult to harvest, due to high ceilings, sheer cliffs and abundance of lava in the nether. One method of mining it is pillaring up to the deposit and extending the top of the column beneath it to make a platform. Mined dust will fall onto the platform, allowing for easy collection.

Breaking this block drops 2-4 pieces of Glowstone Dust, which may be used to re-craft the Glowstone blocks or to boost the effect of a potion. Unlike torches, it isn't destroyed by water and continues to emit light even when submerged like Jack-O-Lanterns. Like all non-sunlight light sources, Glowstone blocks will cause nearby snow and ice to melt.

Uses
Glowstone is an infinite light source and has a higher light level than Torches (15 as opposed to 14.) Because it is a block, players often make ceiling lights and lamp posts out of Glowstone by combining it with a Fence block. Glowstone blocks can also be used as lit paths, due to their interesting texture, or in docks or harbors so players in boats can see where to stop, since it can be placed in water. Also, Glowstone can be used as a source of sunlight for growing crops at night. However, you cannot place anything on glowstone except blocks, meaning iron bars, torches, doors, etc. cannot be placed.

Glowstone can also be used to make Chandeliers.

Put a fence on a ceiling and put glow stones hanging on the fence in any shape you want and put trap doors around it.

History
Glowstone was first introduced in the Halloween Update.

In Beta 1.9 Pre-release 5 changed Glowstone's texture from to.

As of the Beta 1.6.6 update, the tool used to extract Glowstone Dust changed from a sword, when it acted like a glass type block, to a pickaxe, as it was then a stone type block. In the same update, the amount of Glowstone Dust needed to craft a Glowstone Block changed from nine to four, and the amount of Glowstone Dust dropped after destroying a Glowstone Block changed from 1 to a range of 2 to 4. in the 1.0.0/RC2 update, Glowstone returned to being a glass type block.

Glowstone can no longer be powered by redstone due to it being a "glass" block as of 1.0. However, this was changed in snapshot 12w06a to allow it, but it has caused other interesting problems. In addition, you can now craft glowstone lamps when combined with redstone. These can go from powered to off and when off, give no light. See Trivia. In the weekly snapshot 12w21a, you can now purchase it from Villagers.

Trivia

 * Another way of collecting glowstone is to redirect a Ghast's fire ball at a Glowstone deposit, destroying the blocks with the resulting explosion. This could be useful if the Glowstone is very hard to reach.
 * It is more efficient to harvest Glowstone using Silk Touch Enchantment, since one block is equivalent to four Glowstone Dust, while usual harvesting is more likely to drop less than mentioned.
 * Redstone can be put on glowstone, but being a transparent block signals can pass from one block to diagonally another with glowstone "blocking but not blocking" it, making possible nearly instant vertical redstone and new vertical logic gate designs.
 * Since Glowstone Blocks become entities when pushed by pistons, this momentarily stops it from giving off light.
 * Rarely, Glowstone can be found touching the ground if the ceiling it was generated on was extremely low (2-3 blocks of clearance).
 * When glowstone is placed 9 or more blocks above ground level (out of its lighting range), glowstone will actually cast a shadow, despite it being a light-emitting block.
 * When hitting glowstone with a pickaxe enchanted with fortune, glowstone still only drops up to 4 glowstone dust and no more.
 * In the 1.2.5 pre-release, looking at a Glowstone Block in creative mode and pressing the "Pick Block" button will give you/select Glowstone Dust.
 * In Minecraft 1.7.3, Glowstone had to be harvested with an Iron Pickaxe or higher; anything else would break the block and no items would drop from it.

Bugs

 * Altering Glowstone or rails on Glowstone (from Beta 1.8 and before) appears to cause the game to crash. This seems to occur when the rails extend to outside of the render distance.
 * Nether Wart cannot be planted under natural terrain generated glowstone veins regardless of height and obstructions.
 * This has not been verified as a bug, but in both Single Player and Multiplayer, when you have glowstone pushed into the same block as your head, you can see through the ground. You will be able to see hollowed out areas, like dungeons, caves, ravines, and mine shafts. To do this you dig a hole two deep, and pick a direction and go two blocks in that direction, making a sideways "L". Next, you place some redstone wiring and repeaters, making the delay as long as possible. Activate the redstone and quickly go into the hole. The piston will push the glowstone into your head. You can see through the ground, but you won't suffocate.